United Kingdom by-election records
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UK by-election records is an annotated list of notable records from UK Parliamentary by-elections. A by-election occurs when a Member of Parliament resigns, dies, or is disqualified or expelled, and an election is held to fill the vacant seat. A constituency is the seat or division that member represented.
Prior to 1945, electoral competition in the United Kingdom exhibited features that make meaningful comparisons with modern results difficult.
Among the most significant were:
- Frequent interventions and withdrawals of parties in different seats.
- Frequent Coalitions between parties, splits within parties and floor-crossing by members.
- Uncontested elections and truces between parties, in particular during both World Wars.
- Generally more significant competition from independent candidates and minor parties.
- Multi-member seats and University seats.
- Higher frequency of by-elections.
- Generally higher turnouts, although several wartime elections exhibited the lowest recorded turnouts.
- Generally higher variation in size of constituency electorates.
Since 1945, the evolution of a stable three-party system has tended to negate each of the above features so that, broadly speaking, elections are more comparable.
In Northern Ireland, as ever, the pattern of party competition is completely different from that on the mainland and comparisons remain problematic.
Hence, unless otherwise stated records are based on results since the 1945 General Election, and earlier exceptional results are listed separately.
- 1 Glossary
- 2 Numerical records
- 2.1 Largest swings
- 2.2 Largest fall in percentage share of vote
- 2.3 Largest increase in percentage share of vote
- 2.4 Largest winning share of the vote
- 2.5 Lowest winning share of the vote
- 2.6 Lowest share of the vote
- 2.7 Smallest majorities
- 2.8 Turnout
- 2.9 Most candidates
- 2.10 Fewest candidates
- 3 Candidate records
- 3.1 Durable by-election candidates
- 3.2 Former MPs making a comeback at a by-election
- 3.3 Shortest-serving by-election victors
- 3.4 Youngest by-election victors
- 3.5 Oldest by-election victors
- 3.6 First women by-election victors
- 3.7 First ethnic minority by-election victors
- 3.8 First by-election victors from specific religions
- 3.9 By-elections losers awarded seats on disqualification of winner
- 3.10 Two or more former MPs contest by-election
- 4 Frequency and duration records
- 4.1 Longest period without a by-election
- 4.2 Longest period between a vacancy arising and a by-election writ being moved
- 4.3 Longest period without a seat changing hands
- 4.4 Longest period between by-election gains for a party
- 4.5 Longest period between by-election holds for a party
- 4.6 Longest period without an opposition gain
- 4.7 Most by-elections in one day
- 4.8 Most by-election losses in one day
- 4.9 Seats with more than one by-election in a single Parliament
- 4.10 By-election days
- 4.11 Countermanded Poll
- 4.12 Seats Left Vacant
- 5 Causes of by-elections
- 5.1 By-elections prompted by assassination
- 5.2 By-elections prompted by accidental death
- 5.3 By-elections prompted by suicide
- 5.4 By-elections prompted by posthumous election of MP
- 5.5 By-elections prompted by scandal
- 5.6 By-elections prompted to provide seat for seat-less personality
- 5.7 By-elections prompted by party splits or disputes
- 5.8 By-elections resulting from Members seeking re-election over a single issue
- 5.9 By-elections to ratify a change of party
- 5.10 By-elections triggered when member leaves on principle
- 5.11 By-elections prompted by Member's desire to contest another seat
- 5.12 By-elections caused by the previous result being declared void
- 5.13 By-elections prompted by disqualification of the sitting Member
- 5.14 By-elections prompted by expulsion from the House
- 5.15 By-elections prompted by lunacy
- 5.16 By-elections prompted by bankruptcy
- 5.17 By-elections prompted for miscellaneous reasons
- 5.18 By-elections prompted by death of member on wartime active service
- 6 Miscellaneous records
- 6.1 Incumbents fall directly from first place to third place
- 6.2 Incumbent Government gains seats
- 6.3 Principal Opposition loses seats
- 6.4 By-election holds overturned at next general election
- 6.5 By-election victors had not contested previous general election
- 6.6 Incumbent party did not contest
- 6.7 Losers had been unopposed at previous election
- 6.8 Major party did not run
- 6.9 Victories by minor parties
- 6.10 Miscellaneous notable results
- 7 By-elections having national significance
- 8 Firsts and lasts
- 9 See also
- 10 References
- 11 Further reading
For comparison purposes the following definitions have been adopted.
- Gain - victory by a party that was not victorious at the immediate previous election
- Loss - defeat of a party that was victorious at the immediate previous election
- Hold - victory by a party that was victorious at the immediate previous election
- Win - victory by a party. ambiguous term that could mean either a gain or a hold
- Incumbent - the party that held the seat at the immediately previous election, irrespective of any intervening change of candidate or candidate's change of party
- Third party - In England, since 1922, the "third party" has been the Liberal Party and its successor, the Liberal Democrats. Additionally, in Scotland and Wales the Scottish National Party (SNP) and Plaid Cymru are also considered to be third parties. Prior to 1922, the third party was the Labour Party.
- Minor party - parties smaller than the third party
- Uncontested - an election where only one candidate is put forward. No votes are actually cast and the candidate is by definition the victor.
For more information about what is meant by the term "swing", see Swing (politics)
1 By-elections where the seat was held by the incumbent MP.
2 By-elections where the seat was held by the incumbent party.
3 By-elections contested by the incumbent MP, who failed to gain re-election.
A party's share of the vote at a general election is not always matched at subsequent by-elections, but given the five-year maximum term of a Parliament, reductions of 20% or more are unusual. Those of 25% or more are listed below:
Worst results for other parties:
|Belfast South by-election, 1982||22.4||UUP||UUP hold|
|Heywood and Middleton by-election, 2014||17.6||Liberal Democrat||Labour hold|
|Glasgow North East by-election, 2009||14.0||Socialist Labour||Labour gain from Speaker|
|Copeland by-election, 2017||9.0||UKIP||Conservative gain from Labour|
|Kinross and West Perthshire by-election, 1963||7.7||SNP||Conservative hold|
|Newry and Armagh by-election, 1986||7.7||Sinn Féin||SDLP gain from Ulster Unionist|
|Swansea East by-election, 1963||5.3||Plaid Cymru||Labour hold|
|Ernest Everard Gates||Conservative||Middleton and Prestwich by-election, 1940||32,036||98.7|
|Ian Paisley||DUP||North Antrim by-election, 1986||33,937||97.4|
|John Craik-Henderson||Conservative||Leeds North East by-election, 1940||23,882||97.1|
|James Milner||Labour||Leeds South East by-election, 1929||11,804||95.8|
|John Mackintosh McLeod||Conservative||Glasgow Central by-election, 1915||5,341||95.3|
|John Taylor||UUP||Strangford by-election, 1986||32,627||94.2|
|Clifford Forsythe||UUP||South Antrim by-election, 1986||30,087||94.1|
Winning shares of the vote below 35%, since 1918:
|Henry Strauss||Conservative||Combined English Universities by-election, 1946||5,483||30.0|
|Mike Thornton||Liberal Democrat||Eastleigh by-election, 2013||13,342||32.1|
|Edward Taswell Campbell||Conservative||Bromley by-election, 1930||12,782||32.4|
|George Machin||Labour||Dundee East by-election, 1973||14,411||32.7|
|Roy Jenkins||Social Democratic||Glasgow Hillhead by-election, 1982||10,106||33.4|
|Guy Barnett||Labour||South Dorset by-election, 1962||13,783||33.5|
|James Carmichael||Ind. Labour Party||Glasgow Bridgeton by-election, 1946||6,351||34.3|
|Leah Manning||Labour||Islington East by-election, 1931||10,591||34.7|
|Kenneth Lindsay||National Labour||Kilmarnock by-election, 1933||12,577||34.8|
|Parmjit Singh Gill||Liberal Democrat||Leicester South by-election, 2004||10,274||34.9|
The Stockport by-election, 1920, was held to elect two MPs. The winners' shares of the total vote were 25.6% and 25.1%. However, as each voter could cast two votes, the situation is not readily comparable to other by-elections in this period.
At the Sheffield Attercliffe by-election, 1909, the winning candidate took only 27.5% of the vote.
Major parties winning 2% or less share of votes cast in a by-election, since 1918:
|Geoff Juby||Liberal Democrat||Rochester and Strood by-election, 2014||349||0.9|
|Roger Goodfellow||Liberal||Glasgow Camlachie by-election, 1948||312||1.2|
|John Scott Duckers||Liberal||Westminster Abbey by-election, 1924||291||1.3|
|Andrew Graham||Liberal Democrat||Clacton by-election, 2014||483||1.3|
|Hugh Annand||Liberal Democrat||South Shields by-election, 2013||352||1.4|
|Elizabeth Jones||UKIP||Tooting by-election, 2016||507||1.6|
|Robert McCreadie||Social and Liberal Democrats||Glasgow Central by-election, 1989||411||1.6|
|Patrick Davies||Labour||Winchester by-election, 1997||944||1.7|
|Ian Miller||Liberal||Glasgow Pollok by-election, 1967||735||1.9|
|Steve Billcliffe||Labour||Newbury by-election, 1993||1,151||2.0|
The worst Conservative performance was in the North Down by-election, 1995, where they took 2.1% of the votes cast. The 'continuation' Social Democratic Party (SDP) took 0.4% of the vote at both the Upper Bann by-election, 1990 and the Bootle by-election the following week.
Candidates winning fewer than ten votes
- Since 1918:1
|5||Bill Boaks||Public Safety Democratic Monarchist White Resident||Glasgow Hillhead by-election, 1982|
|5||Smiley Smilie||Independent||Tooting by-election, 2016|
|5||Kailash Trivedi||Independent Janata Party||Kensington by-election, 1988|
|7||John Connell||Peace - stop ITN manipulation||Chesterfield by-election, 1984|
|8||Esmond Bevan||Systems Designer2||Bermondsey by-election, 1983|
|8||Tony Farnon||Independent||Haltemprice and Howden by-election, 2008|
|8||Norman Scarth||Independent||Haltemprice and Howden by-election, 2008|
|9||Bobby Smith||Bring Back Elmo||Tooting by-election, 2016|
- 1 F. R. Lees, a Temperance Chartist, won no votes in the Ripon by-election, 1860, as his supporters mistakenly believed that he had withdrawn.
- 2 Bevan made a mistake when filling in his nomination paper and put his occupation ("Systems Designer") in the space labelled description, which was printed on the ballot paper then. He was an independent candidate.
All majorities of less than 1,000 since the Second World War. Bold entries indicate a new record.
Still smaller majorities have been recorded since 1918. The majority in the Penrith and Cockermouth by-election, 1921, was only 31 votes, and in the Westminster Abbey by-election, 1924 was 43 votes. At the Cirencester by-election, 1892 a majority of 3 for the Unionists was overturned on petition, where it was found that both candidates had an equal number of votes. A fresh by-election was called, which was won by the Liberals.
Turnout is recorded as the percentage of valid votes from the total recorded vote.
The highest turnouts since 1918.
|Mid Ulster by-election, 1969||1969||91.5%|
|Mid Ulster by-election, 1955||1955||89.7%|
|Ashton-under-Lyne by-election, 1928||1928||89.1%|
|Fermanagh and South Tyrone by-election, August 1981||1981||88.6%|
|Mid Ulster by-election, 1956||1956||88.4%|
|Tiverton by-election, 1923||1923||88.1%|
|Darlington by-election, 1926||1926||87.6%|
|Carmarthen by-election, 1957||1957||87.4%|
|Fermanagh and South Tyrone by-election, April 1981||1981||86.9%|
|Stockport by-election, 1925||1925||85.7%|
|Brighouse and Spenborough by-election, 1950||1950||85.4%|
Turnout increased from general election
It is highly unusual for a by-election to attract a higher turnout in a seat than the previous general election.
During the Second World War the electoral register was not kept up to date despite significant population movements, especially in the London area (which contains all three constituencies listed below). Consequently, only those eligible to vote in the constituency at the outbreak of war were eligible to vote in the by-elections and many voters were physically unable to as they were located elsewhere; in addition the major parties did not compete against each other. The lowest turnout in peacetime since 1918 was 18.2% at the Manchester Central by-election, 2012. The lowest turnouts since 1918 have been:
- Poplar South by-election, 1942: 9.3%
- Harrow by-election, 1941: 10.7%
- Camberwell North by-election, 1944: 11.2%
Turnouts of less than 30% since 1945 (bold indicates a new post-war record)
|Manchester Central by-election, 2012||18.2%|
|Leeds Central by-election, 1999||19.6%|
|Shoreditch and Finsbury by-election, 1958||24.9%|
|Wigan by-election, 1999||25.0%|
|Tottenham by-election, 2000||25.4%|
|Cardiff South and Penarth by-election, 2012||25.7%|
|Batley and Spen by-election, 2016||25.8%|
|Newham South by-election, 1974||25.9%|
|Middlesbrough by-election, 2012||26.0%|
|Croydon North by-election, 2012||26.5%|
|West Bromwich West by-election, 2000||27.6%|
|Feltham and Heston by-election, 2011||28.8%|
|Preston by-election, 2000||29.6%|
|Kensington and Chelsea by-election, 1999||29.7%|
Under current UK electoral law there is no upper or lower limit for candidature numbers, with the only required stipulation being the valid nomination of ten electors from the constituency. By-elections often attract "fringe" or novelty candidates, single-issue candidates, or independents. As with nominations in a general election, candidates must pay a £500 deposit, which is only refunded if the candidate wins 5% of the votes cast.
All by-elections with more than ten candidates are listed. Elections are listed in alphabetical order. Those that created a new record number appear in bold.
In 2017, the countermanded poll in Manchester Gorton had 11 candidates.
|Year||Number of candidates||Election|
|1986||2||Eight of the Northern Ireland by-elections2|
|1981||Fermanagh and South Tyrone|
- *1 The most recent mainland UK example
- *2 Four of the eight straight fights were between the Unionist incumbent and a "paper candidate" using the name "Peter Barry", the name of the then Irish Minister of Foreign Affairs.
Durable by-election candidates
Former Labour cabinet minister Tony Benn contested no fewer than four by-elections during his career, topping the poll on each occasion: Bristol South East in 1950, 1961 and 1963, and Chesterfield in 1984. His first and last by-election victories were 33 years and 3 months apart.
Former cabinet minister and European Commissioner Roy Jenkins fought two different by-elections for the Social Democratic Party only eight months apart. He narrowly failed in the Warrington by-election, 1981 before winning the Glasgow Hillhead by-election, 1982. He had been first elected as a Labour MP almost 34 years previously in the Southwark Central by-election, 1948.
Former Speaker of the House of Commons, Betty Boothroyd finally secured election at her third by-election attempt at the West Bromwich by-election, 1973. She had previously failed in the Leicester South East by-election, 1957 and the Nelson and Colne by-election, 1968 as well as the General Elections of 1959 and 1970.
John Bickley of UKIP contested three by-elections (all in Greater Manchester) within two years - Wythenshawe and Sale East in February 2014, Heywood and Middleton in October 2014 and Oldham West and Royton in December 2015. He was defeated on each occasion, coming closest in Heywood and Middleton where he lost by less than 700 votes. Bickley also contested Heywood and Middleton at the 2015 general election, making a total of four parliamentary elections contested in less than 24 months.
Minor parties and independents
Perennial fringe candidates include such personalities as Bill Boaks, whose highest vote was at the Beaconsfield by-election, 1982 with 99 votes. Screaming Lord Sutch was for most of his career the leader of the Official Monster Raving Loony Party. His highest vote total was 1,114 at the Rotherham by-election, 1994. Lindi St Clair of the Corrective Party contested eleven by-elections without success, her highest total being 216 votes as 'Lady Whiplash' at the Eastbourne by-election, 1990. Sutch's successor as leader of the Official Monster Raving Loony Party, Alan "Howling Laud" Hope, has also contested eleven by-elections.
John Cartwright of the Official Monster Raving Loony Party has contested three by-elections without success, his most successful total being 188 at the Ealing Southall by-election, 2007. Under various ballot paper descriptions, David Bishop of the Church of the Militant Elvis label has stood at five by-elections, getting 99 votes at the Corby by-election, 2012, an increase over his previous high of ninety-three at Feltham and Heston by-election, 2011.
Joseph Gibbins is the only person in modern times to gain the same seat twice in two different by-elections. He triumphed for Labour in the Liverpool West Toxteth by-election, 1924 and the Liverpool West Toxteth by-election, 1935.
Prime Minister Winston Churchill contested five by-elections in his long career:-
- Oldham by-election, 1899 in which he was not elected
- Manchester North West by-election, 1908 where he was defeated
- Dundee by-election, 1908 where he was elected
- Dundee by-election, 1917 where he was re-elected.
- Westminster Abbey by-election, 1924 in which he was unsuccessful
John Wilkes won the Aylesbury by-election, 1757, and was then elected in the Middlesex by-elections of February, March and April 1769, on each occasion being subsequently expelled from the House of Commons.
Former MPs making a comeback at a by-election
|Bradford West by-election, 20121||George Galloway||Respect||returns after failing to win a seat in the 2010 General Election|
|South Antrim by-election, 20001||William McCrea||DUP||returns after losing his Mid Ulster seat in the 1997 General Election.|
|Kensington and Chelsea by-election, 1999||Michael Portillo||Conservative||returns after losing his Enfield Southgate seat at the 1997 General Election.|
|Beckenham by-election, 1997||Jacqui Lait||Conservative||returns after losing her Hastings and Rye seat at the 1997 General Election.|
|Epping Forest by-election, 1988||Steve Norris||Conservative||returns after losing his Oxford East seat at the 1987 General Election.|
|Glasgow Govan by-election, 19881||Jim Sillars||SNP||He had first sat as a Labour MP (later as Scottish Labour) for South Ayrshire between 1970 and 1979.|
|Chesterfield by-election, 1984||Tony Benn||Labour||returns after losing his redrawn Bristol East seat at the 1983 General Election.|
|Beaconsfield by-election, 1982||Tim Smith||Conservative||returns after losing his Ashfield seat in the 1979 General Election.|
|Glasgow Hillhead by-election, 19822:||Roy Jenkins||Social Democratic||returns after a spell as European Commissioner, then co-founding the Social Democratic Party (SDP). He had first sat as a Labour MP for Southwark Central from 1948–50 and Birmingham Stechford from 1950-77.|
|Crosby by-election, 19811||Shirley Williams||Social Democratic||returns as the first-elected SDP MP. She had first sat as a Labour MP for Hitchin 1964-74 and for Hertford and Stevenage 1974-79|
|Warrington by-election, 1981||Douglas Hoyle||Labour||returns after losing his Nelson and Colne seat in the 1979 General Election.|
|Southend East by-election, 1980||Teddy Taylor||Conservative||returns after losing his Glasgow Cathcart seat at the 1979 General Election|
|South West Hertfordshire by-election, 1979||Richard Page||Conservative||returns after losing his Workington seat in the 1979 General Election|
|Knutsford by-election, 1979||Jock Bruce-Gardyne||Conservative||returns after losing his South Angus seat at the October 1974 General Election.|
|Clitheroe by-election, 1979||David Waddington||Conservative||returns after losing his Nelson and Colne seat at the October 1974 General Election.|
|Glasgow Garscadden by-election, 1978||Donald Dewar||Labour||returns after losing his Aberdeen South seat in the 1970 General Election.|
|Newham South by-election, 1974||Nigel Spearing||Labour||returns after losing his Acton seat in the February 1974 General Election.|
|Merthyr Tydfil by-election, 19722||Edward Rowlands||Labour||returns after losing his Cardiff North seat in the 1970 General Election.|
|Greenwich by-election, 1971||Guy Barnett||Labour||returns after losing his South Dorset seat in the 1964 General Election.|
|Southampton Itchen by-election, 1971||Bob Mitchell||Labour||returns after losing his Southampton Test seat in the 1970 General Election.|
|St Marylebone by-election, 1970||Kenneth Baker||Conservative||returns after losing his Acton seat in the 1970 General Election.|
|Chichester by-election, 1969||Christopher Chataway||Conservative||returns after losing his Lewisham North seat in the 1966 General Election.|
|Brighton Pavilion by-election, 1969||Julian Amery||Conservative||returns after losing his Preston North seat in the 1966 General Election.|
|New Forest by-election, 1968||Patrick McNair-Wilson||Conservative||returns after losing his Lewisham West seat in the 1966 General Election.|
|Warwick and Leamington by-election, 1968||Dudley Smith||Conservative||returns after losing his Brentford and Chiswick seat in the 1966 General Election.|
|West Derbyshire by-election, 1967||James Scott-Hopkins||Conservative||returns after losing his Cornwall North seat in the 1966 General Election.|
|Brierley Hill by-election, 1967||Fergus Montgomery||Conservative||returns after losing his Newcastle upon Tyne East seat in the 1964 General Election.|
|Honiton by-election, 1967||Peter Emery||Conservative||returns after losing his Reading seat in the 1966 General Election.|
|Saffron Walden by-election, 1965||Peter Kirk||Conservative||returns after losing his Gravesend seat in the 1964 General Election.|
|Salisbury by-election, 1965||Michael Hamilton||Conservative||returns after losing his Wellingborough seat in the 1964 General Election.|
|East Grinstead by-election, 1965||Geoffrey Johnson-Smith||Conservative||returns after losing his Holborn and St. Pancras South seat in the 1964 General Election.|
|Altrincham and Sale by-election, 1965||Anthony Barber||Conservative||returns after losing his Doncaster seat in the 1964 General Election.|
|St Marylebone by-election, 1963||Quintin Hogg||Conservative||returns after disclaiming his peerage. He had previously sat for Oxford 1938-1950.|
|Kinross and West Perthshire by-election, 1963||Sir Alec Douglas-Home||Conservative||returns after disclaiming his peerage. He had previously sat for Lanark 1931-45 and 1950-51.|
|Bristol South East by-election, 1963||Tony Benn||Labour||returns after disclaiming his peerage. He had been disqualified after the death of his father in 1960, and his election in a 1961 by-election had been adjudged undue on petition.|
|Middlesbrough East by-election, 1962||Arthur Bottomley||Labour||returns after losing his Rochester and Chatham seat in the 1959 General Election.|
|Ebbw Vale by-election, 1960||Michael Foot||Labour||returns after losing his Plymouth Devonport seat in the 1955 General Election.|
|Newport by-election, 1956||Frank Soskice||Labour||returns after his Sheffield Neepsend seat was abolished at the 1955 General Election.|
|Sheffield Neepsend by-election, 1950||Frank Soskice||Labour||returns after his Birkenhead East seat was abolished at the 1950 General Election.|
|Houghton-le-Spring by-election, 19131||Thomas Edward Wing||Liberal||returns after losing his Grimsby seat at the December 1910 General Election.|
|Bootle by-election, 1911||Bonar Law||Conservative||returns after failing to win Manchester North-West in the December 1910 General Election.|
|Dundee by-election, 1908||Winston Churchill||Liberal||returns after losing his Manchester North West seat in a 1908 by-election, upon his appointment to the Board of Trade.|
|Dulwich by-election, 1906||Bonar Law||Conservative||returns after losing his Glasgow Blackfriars and Hutchesontown seat in the 1906 General Election.|
|City of London by-election, February 1906||Arthur Balfour||Conservative||returns after losing his Manchester East seat in the 1906 General Election.|
1 by-election gain lost at the subsequent General Election
2 by-election gain held at the subsequent General Election
Former MPs failing in a by-election
- Richmond Park by-election, 2016 - Incumbent Richmond Park MP Zac Goldsmith stands as an independent Conservative to protest against a third runway at Heathrow. He loses to the Liberal Democrats.
- Haltemprice and Howden by-election, 2008 - Former Vale of Glamorgan MP Walter Sweeney stands as an independent, winning 1% of the votes.
- Cheadle by-election, 2005: Stephen Day fails to regain for the Conservatives a seat he lost by only 33 votes four years previously.
- Winchester by-election, 1997: Gerald Malone fails to regain the seat for the Conservatives, after losing by only 2 votes six months previously.
- Christchurch by-election, 1993: Robert Hayward loses one of the Conservatives' safest seats to the Liberal Democrats.
- Eastbourne by-election, 1990: Richard Hickmet fails to defend the seat for the Conservatives, after publicly stating that for electors not to support him would be a moral victory for the Provisional Irish Republican Army.
- Pontypridd by-election, 1989: Tom Ellis, former Labour and SDP MP, stands for the Social and Liberal Democrats, losing his deposit.
- Fermanagh and South Tyrone by-election, 1986: Owen Carron fails to regain the seat for Sinn Féin that he held 1981-83.
- Peckham by-election, 1982: Dick Taverne, former Labour and Democratic Labour MP, stands for the SDP, fails to take Labour seat.
- Gower by-election, 1982: Gwynoro Jones, former Labour MP, stands for the SDP,fails to take Labour seat.
- Beaconsfield by-election, 1982: Paul Tyler fails for the Liberals in a by-election held during the Falklands War.
- Warrington by-election, 1981: Roy Jenkins narrowly fails to win for the SDP from Labour in its first parliamentary contest.
- Fermanagh and South Tyrone by-election, April 1981: Harry West fails to regain his old seat against Bobby Sands
- Hamilton by-election, 1978: Margo Macdonald fails to repeat the SNP's 1967 triumph.
- Ilford North by-election, 1978: Thomas Iremonger, who had sat for the seat 1954-74, stands as an independent Conservative, winning a mere 1.5% of the vote.
- Birmingham Stechford by-election, 1977: Terry Davis loses a safe Labour seat.
- Walsall North by-election, 1976: David Winnick loses a safe Labour seat.
- Liverpool Scotland by-election, 1971: Peter Mahon stands as an Independent Labour Anti-Abortion candidate, securing 10.3% of the vote.
- Brighton Pavilion by-election, 1969: Thomas Skeffington-Lodge stands for Labour in a safe Conservative seat, 19 years after losing his seat.
- Nuneaton by-election, 1967: Air Vice-Marshal Donald Bennett stands as a National Party candidate, 22 years after losing his seat as a Liberal MP.
- Salisbury by-election, 1965: Horace Trevor-Cox stands as an independent Conservative, 20 years after losing his seat.
- Leyton by-election, 1965: Patrick Gordon-Walker narrowly loses a supposed safe seat.
- South Dorset by-election, 1962: Angus Maude narrowly loses.
- Bolton East by-election, 1960: Frank Byers stands for the Liberals.
- Hereford by-election, 1956: Frank Owen fails to regain for the Liberals the seat he previously sat for 1929-1931.
- Mid Ulster by-election, 1956: Michael O'Neill fails to regain the seat, a year after retiring as its MP.
- Croydon North by-election, 1948: Air Vice-Marshal Donald Bennett stands for the Liberals, losing his deposit, and Harold Nicolson, for Labour, but fail to take a Conservative seat three years after both lost their respective seats.
- Hornsey by-election, 1941, Hampstead by-election, 1941 and two others: Noel Pemberton Billing fails to take a seat, 20 years after standing down as an independent MP.
- Westminster Abbey by-election, 1924: Winston Churchill narrowly fails to take the seat, as a Constitutionalist.
- Anglesey by-election, 1923: Edward Thomas John failed to defend the seat.
- Woolwich East by-election, 1921: Ramsay MacDonald loses a supposed safe Labour seat.
- Westminster Abbey by-election, 1921: Arnold Lupton failed to take a Conservative seat, coming third, ten years after standing down.
- Cardiganshire by-election, 1921: W. Llewelyn Williams defeated in this race, as anti-Coalition Liberal contesting against a Coalition Liberal, three years after abolition of his previous seat.
- Dartford by-election, 1920: Thomas Edward Wing failed to defend the seat, over a year after losing his previous seat, losing it to Labour.
Re-election of Ministers
Until the Re-election of Ministers Acts 1919 and 1926 there were many cases of members having to seek re-election on appointment to ministerial office. In eight instances they were unsuccessful:
- Pontypridd by-election, 1922 Thomas Arthur Lewis was defeated after being appointed a Junior Lord of the Treasury.
- Dudley by-election, 1921 Sir Arthur Griffith-Boscawen was defeated after being appointed Minister of Agriculture.
- Ipswich by-election, 1914 Charles Masterman was defeated in a subsequent attempt to return to the House of Commons.
- Bethnal Green South West by-election, 1914 Charles Masterman was defeated after being appointed Chancellor of the Duchy of Lancaster.
- Manchester South by-election, 1912 Sir Arthur Haworth was defeated after being appointed a Junior Lord of the Treasury.
- North Ayrshire by-election, 1911 Andrew Macbeth Anderson was defeated after being appointed Solicitor General for Scotland.
- Manchester North West by-election, 1908 Winston Churchill was defeated after being appointed President of the Board of Trade
- Brighton by-election, 1905 Gerald Loder was defeated after being appointed Lord Commissioner of the Treasury
Shortest-serving by-election victors
- Bobby Sands, Anti-H Block Fermanagh and South Tyrone by-election, April 1981 25 days 1
- Michael Carr, Labour Bootle by-election, May 1990 57 days 1
- Oswald O'Brien, Labour Darlington by-election, 1983 77 days 2
- Margo Macdonald, SNP Glasgow Govan by-election, 1973 112 days 2
- Charles Beattie, Unionist Mid Ulster by-election, 1955 123 days 3
- Mark Reckless, UKIP Rochester and Strood by-election, 2014 130 days 2b
- Nicol Stephen, Lib Dem Kincardine and Deeside by-election, 1991 154 days 2
- Ashok Kumar, Labour Langbaurgh by-election, 1991 154 days 2a
- Helen McElhone, Labour Glasgow Queen's Park by-election, 1982 189 days 4
- David Austick, Liberal Ripon by-election, 1973 217 days 2
- John Spellar, Labour Birmingham Northfield by-election, 1982 224 days 2a
- Christopher Ward, Conservative Swindon by-election, 1969 231 days 2
- William McCrea, DUP South Antrim by-election, 2000 259 days 2ab
- Parmjit Singh Gill, Lib Dem Leicester South by-election, 2004 294 days 2
- David Colville Anderson, Conservative Dumfriesshire by-election, 1963 309 days 5
- Huw Edwards, Labour Monmouth by-election, 1991 329 days 2a
- Thomas Teevan, Unionist Belfast West by-election, 1950 330 days 2
- Wallace Lawler, Liberal Birmingham Ladywood by-election, 1969 357 days 2
- George Machin, Labour Dundee East by-election, 1973 364 days 2
- 1 died
- 2 defeated at next general election
- 3 disqualified (Beattie was never elected. He was awarded the seat on the disqualification of his predecessor, only to be found to be disqualified himself)
- 4 retired at next general election (seat abolished by redistribution and failed to secure alternative seat)
- 5 retired at next general election due to personal difficulties
- a returned to Parliament at a subsequent election
- b had served previously as an MP
- Henry Francis Compton, Conservative New Forest by-election, 1905 46 days 2
- Ronald Bell, Conservative Newport by-election, 1945 70 days 2a
- Donald Bennett, Liberal Middlesbrough West by-election, 1945 73 days 2
- John Dumphreys, Conservative Bermondsey by-election, 1909 83 days 2
- Seaborne Davies, Liberal Caernarvon Boroughs by-election, 1945 91 days 2
- Joseph Ormond Andrews, Liberal Barkston Ash by-election, 1905 97 days 2
- Dr Robert McIntyre, SNP Motherwell by-election, 1945 104 days 2
- Ruth Dalton, Labour Bishop Auckland by-election, 1929 112 days 3
- George Knox Anderson, Conservative Canterbury by-election, 1918 113 days 3
- Herbert Evans, Labour Gateshead by-election, 1931 121 days 1
- Andrew Clarke, Labour Midlothian and Peebles North by-election, 1929 121 days 2b
- Sir Henry Wilson, Unionist North Down by-election, February 1922 121 days 5
- Joseph Henderson, Labour Manchester Ardwick by-election, 1931 135 days 2a
- Evan Cotton, Liberal Finsbury East by-election, 1918 151 days 2
- David Hardie, Labour Glasgow Rutherglen by-election, 1931 159 days 2
- Lord Arthur Hill, Unionist West Down by-election, 1907 193 days 7b
- Oswald Cawley, Liberal Prestwich by-election, January 1918 202 days 1
- Francis Norie-Miller, Liberal National Perth by-election, 1935 212 days 3
- George Banton, Labour Leicester East by-election, 1922 230 days 2a
- William Henry Somervell, Liberal Keighley by-election, 1918 232 days 2
- Noel Edward Buxton, Liberal Whitby by-election, 1905 238 days 2a
- Leslie Orme Wilson, Conservative Portsmouth South by-election, 1922 243 days 7b
- Leah Manning, Labour Islington East by-election, 1931 250 days 2a
- Frederick William Gibbins, Liberal Mid Glamorgan by-election, 1910 253 days 3
- C. V. F. Palmer, Independent The Wrekin by-election, 1920 261 days 1
- Maurice Healy, Ind. Nationalist Cork City by-election, 1909 262 days 2ab
- John Edward Sutton, Labour Manchester Clayton by-election, 1922 270 days 2ab
- James Chuter Ede, Labour Mitcham by-election, 1923 278 days 2a
- J. J. Cleary, Labour Liverpool Wavertree by-election, 1935 281 days 2
- Sir William Beveridge, Liberal Berwick-upon-Tweed by-election, 1944 282 days 2
- W. P. Sidney, Conservative Chelsea by-election, 1944 288 days 4
- Sir John Reith, National Southampton by-election, February 1940 293 days 6
- W. E. Gibbons, Conservative Bilston by-election, 1944 309 days 2
- Lord Charles Beresford, Conservative Woolwich by-election, 1902 320 days 7ab
- Arthur Henderson, Labour Newcastle East by-election, 1923 323 days 2ab
- James Henry Hall, Labour Whitechapel and St.George's by-election, 1931 328 days 2a
- Thomas Naylor, Labour Southwark South East by-election, 1921 336 days 2a
- 1 died
- 2 defeated at next general election
- 3 retired at next general election
- 4 retired at next general election, upon succession to a peerage
- 5 assassinated by IRA
- 6 elevated to the Peerage
- 7 resigned
- a returned to Parliament at a subsequent election
- b had served previously as an MP
Youngest by-election victors
- Esmond Harmsworth, elected on 15 November 1919 from Isle of Thanet aged 21 years 170 days.
- Youngest woman: Bernadette Devlin, elected on 17 April 1969 from Mid Ulster aged 21 years 359 days.
Babies of the House elected at by-elections
Oldest by-election victors
Debuts in Parliament:
- Hucks Gibbs was 71 when he held the City of London by-election, April 1891 for the Conservatives.
- Sir Robert Pullar was 79 (less 6 days) when he held the Perth by-election, 1907 for the Liberals.
- David Cleghorn Hogg was 73 when he gained the Londonderry City by-election, 1913 for the Liberals.
- Sir Swire Smith was 73 when he held the Keighley by-election, 1915 for the Liberals.
- William Frederick Hicks Beach was 74 when he held the Tewkesbury by-election, 1916 for the Conservatives.
- Sir George Reid was 70 when he held the St George's, Hanover Square by-election, 1916 for the Conservatives. He was a former Prime Minister of Australia.
- George Edwards was almost 70 when he gained the South Norfolk by-election, 1920 for Labour. He was an agricultural labourer.
- Henry Bruce Armstrong was almost 77 when he held the Mid Armagh by-election, 1921 for the Ulster Unionists.
- William Nathaniel Jones was 70 when he held the Carmarthen by-election, 1928 for the Liberals.
- Francis Norie-Miller was 76 when he gained the Perth by-election, 1935 for the Liberal Nationals.
- John Evans was 70 when he held the Ogmore by-election, 1946 for Labour.
Comebacks to Parliament:
- James Patrick Mahon was 79 when he held the Clare by-election, 1879 and 87 when he held the County Carlow by-election, 1887 for the Irish Nationalists.
- Sir Wilfrid Lawson was 74 when he held the Camborne by-election, 1903 for the Liberals.
- Sir Alfred Hopkinson was 74 when he won the Combined English Universities by-election, 1926 for the Conservatives. He had previously been MP for Cricklade 1895-98 before resigning.
- Arthur Salter was 70 when he held the Ormskirk by-election, 1951 for the Conservatives. He had served previously as MP for Oxford University 1937-50 prior to that seat's abolition.
In defence of a previously held seat:
- Enoch Powell was 73 when he successfully defended his seat at the South Down by-election, 1986 for the Ulster Unionists, after a protest resignation against the Anglo-Irish Agreement, although he had been an MP almost continuously since 1950.
First women by-election victors
Note 1 Mabel Philipson succeeded her husband at the Berwick-upon-Tweed by-election, 1923. He had been elected as a National Liberal Party candidate. She won as a Conservative so this could arguably be classed as the first gain by a woman.
First ethnic minority by-election victors
Whilst the first ethnic minority Members of Parliament were elected as early as the 1890s, it would be almost 100 years before one was returned at a by-election.
- David Lammy held the Tottenham by-election, 2000 for Labour.
- Mark Hendrick held the Preston by-election, 2000 for Labour.
- Parmjit Singh Gill gained the Leicester South by-election, 2004 for the Liberal Democrats.
The first by-election in which all three major-party candidates were from the ethnic minorities was the Ealing Southall by-election, 2007, held by Labour.
First by-election victors from specific religions
When the UK Parliament was established in 1801, non-Anglicans were prevented from taking their seats as MPs under the Test Act 1672. However, Methodists took communion at Anglican churches until 1795, and some continued to do so, and many Presbyterians were prepared to accept Anglican communion, thus ensuring that members of these creeds were represented in the Parliament. Some Unitarians were also elected.
The first by-election victor (and first ever MP) to be an adherent of the Eastern Orthodox Church was The Honourable Frederick North who was elected in 1792 for Banbury (to succeed his father who had entered the House of Lords), having converted to the faith the previous year.
The first atheist by-election victor was Charles Bradlaugh, at the Northampton by-election, 1881. As an atheist, Bradlaugh was not allowed to swear the Oath of Allegiance, and the by-election was re-run in 1882 and 1884. Both were also won by Bradlaugh, who eventually was able to take his seat after the 1885 general election.
- David Salomons was the first Jewish by-election victor, at the Greenwich by-election, 1851.
- Terry Rooney was the first Mormon by-election victor, at the Bradford North by-election, 1990.
- Parmjit Singh Gill became the first Sikh by-election victor, at the Leicester South by-election, 2004.
- Virendra Sharma became the first Hindu by-election victor, at the Ealing Southall by-election, 2007.
- Rosena Allin-Khan was the first Muslim by-election victor, at the Tooting by-election, 2016.
By-elections losers awarded seats on disqualification of winner
- Malcolm St Clair, Bristol South East by-election, 1961 (resigned in 1963 to enable another by-election)
- Charles Beattie, Mid Ulster by-election, 1955 (he too was disqualified a few weeks later, causing another by-election)
Two or more former MPs contest by-election
- Haltemprice and Howden by-election, 20081
- Winchester by-election, 1997
- Fermanagh and South Tyrone by-election, 1986
- Beaconsfield by-election, 1982
- Warrington by-election, 1981
- Brighton Pavilion by-election, 1969
- Salisbury by-election, 1965
- Mid Ulster by-election, 1956
- Croydon North by-election, 1948
- Altrincham by-election, 1933 (three former MPs)
- Glasgow Shettleston by-election, 1930
- Nottingham Central by-election, 1930 (three former MPs)
- Cheltenham by-election, 1928
1 Conservative MPs David Davis and Walter Sweeney
Frequency and duration records
Longest period without a by-election
All periods of over a year between by-elections are listed:
- 20 November 1997 - 10 June 1999: 567 days
- 7 November 1991 - 6 May 1993: 546 days
- 12 March 1987 - 14 July 1988: 489 days
- 14 February 2002 - 18 June 2003: 489 days
- 12 November 2009 - 13 January 2011: 427 days
- 23 May 1974 - 26 June 1975: 399 days
- 18 June 2003 - 15 July 2004: 393 days
- 29 June 2006 - 19 July 2007: 385 days
- 1992, 1998 and 2010 are the only calendar years in history without a single by-election. Since 1992 and 2010 were nonetheless general election years, 1998 stands as the only year in British history without any parliamentary election.
Longest period between a vacancy arising and a by-election writ being moved
- The Wrekin by-election, 1941: 357 days. James Baldwin-Webb was presumed killed as a result of enemy action when SS City of Benares was torpedoed on 17 September 1940; the writ was moved on 9 September 1941.
- King's Norton by-election, 1941: 327 days. Ronald Cartland was killed in action on 29–30 May 1940. Initially posted missing, his death was not presumed until January 1941. The writ was moved on 22 April 1941.
- Hitchin by-election, 1941: 272 days. Sir Arnold Wilson was presumed killed in action on 31 May 1940; the writ was moved on 27 February 1941.
- Newcastle-under-Lyme by-election, 1969: 236 days. Stephen Swingler died on 19 February 1969; the writ was moved on 13 October 1969.
- Swindon by-election, 1969: 220 days. Francis Noel-Baker resigned on 7 March 1969; the writ was moved on 13 October 1969.
Longest period without a seat changing hands
The longest period without a seat changing hands in a by-election was the five years between the Conservative victories in the Glasgow Camlachie by-election, 1948 and the Sunderland South by-election, 1953.
During the short Parliaments of 1910, 1950-1 and 1974 no seats changed hands in a by-election.
Longest period between by-election gains for a party
The Liberal Party endured 29 years without a single by-election gain between the Holland and Boston by-election, 1929 and the Torrington by-election, 1958. It did not win a single by-election in the thirteen years between holding the Middlesbrough West by-election, 1945 and gaining Torrington.
Until the Crewe and Nantwich by-election, 2008, the opposition Conservative Party had not gained a seat in almost 26 years, the last being the Mitcham and Morden by-election, 1982, which occurred during the unique circumstances of the Falklands War and the sitting Labour MP defecting to the Social Democratic Party and seeking re-election under his new party label. The Conservatives' last gain while in Opposition was 30 years previously at the Ilford North by-election, 1978.
Note 1 The Labour Party were the official opposition in the Parliament elected in 1935, but after the major parties agreed an electoral truce on the outbreak of war in 1939, they did not contest any Conservative or Liberal seats for the remainder of the Parliament, a period of six years, and were members of the wartime coalition government between May 1940 and May 1945.
Longest period between by-election holds for a party
The Conservatives did not successfully defend a single by-election in the eight years between their holds of the Richmond by-election, 1989 and the Uxbridge by-election, 1997, losing a record 15 consecutive seats where they were the incumbents. By the time of the by-election in Uxbridge, the victor in Richmond, William Hague, had become leader of the Conservative Party.
Labour's worst run was in losing 4 by-elections on the trot, which has occurred three times since 1945:
Longest period without an opposition gain
For a period of 11 years, until the Crewe and Nantwich by-election, 2008, the principal opposition Conservative Party failed to register a by-election gain against the incumbent Labour Government. This is the longest period of such failure since records began, and more than twice the previous record of the five years it took the then Labour opposition to gain the Lewisham North by-election, 1957.
Apart from the brief parliaments of 1910, 1950-1 and 1974, the parliaments of 1951-5 and 1997-2001 are the only occasions when the Government did not lose a by-election.
Most by-elections in one day
The largest number of by-elections held on a single day occurred on 23 January 1986 when 15 simultaneous contests were held in Northern Ireland. The elections had been engineered by the incumbent Unionist parties as a protest against the Anglo-Irish Agreement of 1985. They intended the results to be interpreted as a referendum on the treaty. The elections were boycotted by the main Nationalist parties except in four seats where they had a reasonable prospect of victory. In the event, the Social Democratic and Labour Party gained one seat, Newry and Armagh, from the Ulster Unionist Party.
Apart from the above example, it is common for UK mainland parties to schedule several by-elections on the same day. Motivations include attempting to divide opponents' resources and getting bad news (expected losses) out of the way. Since 1945, the largest number of simultaneous mainland by-elections has been 6, held on 16 November 1960. On four occasions, 5 by-elections have been held on the same day, most recently on 9 June 1994. Groupings of two or three are very common.
Before November 2012, the last day on which three by-elections had been held was 23 November 2000. In November 2012 there were two such groupings of three (15 November and 29 November). The last time there were six by-elections in one calendar month was in June 1994.
Most by-election losses in one day
Occasions since 1945 when two seats have fallen are:
- 7 November 1991
- 4 November 1976
- 8 November 1973
- 26 July 1973
- 2 November 1967
- 21 September 1967
- 22 November 1962
Seats with more than one by-election in a single Parliament
- Bootle: May and November 1990.
- Fermanagh and South Tyrone: April and August 1981.
- Bristol South East: 1961 and 1963.
- Mid Ulster: 1955 and 1956.
- Edinburgh East: 1945 and 1947.
- Middlesbrough West: 1940 and 1945.
- Combined Scottish Universities: 1936, 1938 and 1945.
- Berwick-upon-Tweed: 1941 and 1944.
- Clay Cross: 1936 and 1944.
- West Derbyshire: 1938 and 1944.
- Buckingham: 1937 and 1943.
- Manchester Gorton: 1937 and 1942.
- Dunbartonshire: 1936 and 1941.
- Greenock: 1936 and 1941.
- Doncaster: 1938 and 1941.
- Southampton: February and November 1940.
- Preston: 1936 and 1940.
- Wandsworth Central: 1937 and 1940.
- City of London: 1938 and 1940.
- Combined Scottish Universities: 1934 and 1935.
- Eastbourne: 1932 and 1935.
- Twickenham: 1932 and 1934.
- Portsmouth South: 1922 and 1923.
- North Down: 1921, February and July 1922.
- West Down: 1921 and 1922.
- South Londonderry: 1921 and 1922.
- Louth: 1920 and 1921.
- The Wrekin: February and November 1920.
- Londonderry North: 1919 and 1922.
- Prestwich: January and October 1918.
- Edinburgh and St Andrews Universities: 1916 and 1917.
- St George's Hanover Square: 1913, 1916 and 1918.
- Portsmouth: 1912 and 1916.
- City of London: February and June 1906.
- Oswestry: 1901 and 1904.
- Southport: 1898 and 1899.
- City of London: April and June 1891.
- Buckingham: 1889 and 1891.
- Ayr Burghs: 1888 and 1890.
- Preston: 1881 and February and November 1882.
- Bath: May, June and October 1873.
- South Shropshire: 1866 and 1867.
- East Gloucestershire: January and December 1854.
- Greenwich: 1851 and 1852.
- South Nottinghamshire: 1848 and 1852.
- Buckinghamshire: 1837 and 1839 and 1842 and 1845, within two successive parliaments.
Other seats with by-elections less than five years apart
- Hemsworth: 1991 and 1996.
- Upper Bann: 1986 and 1990.
- Belfast South: 1982 and 1986.
- Fermanagh and South Tyrone: August 1981 and 1986.
- Nuneaton: 1965 and 1967.
- Ormskirk: 1951 and 1953.
- Liverpool Wavertree: 1931 and 1935.
- Twickenham: 1929 and 1932.
- Westminster Abbey: 1921 and 1924.
British Parliamentary elections are invariably held on a Thursday. The last by-election not held on a Thursday was the Hamilton by-election, 1978, held on Wednesday 31 May due to a World Cup opening match on the Thursday evening.
Due to an administrative oversight, the Manchester Exchange by-election, 1973 was held on Wednesday 27 June 1973. Prior to that, the last by-elections not held on a Thursday were the Saffron Walden by-election, 1965 held on Tuesday 23 March, and the Roxburgh, Selkirk and Peebles by-election, 1965 held the following day.
Until the mid-1960s, it was common to hold by-elections on any day of the week (other than Sunday).
Very occasionally, a scheduled by-election may be overtaken by the calling of a general election and the dissolution of Parliament, in which case the poll is countermanded by the Returning Officer. There have been only three occasions since 1918: a by-election was scheduled to take place in Warwick and Leamington on 21 November 1923, but was cancelled by a dissolution of Parliament on 16 November. A by-election was scheduled to poll between 13–17 October 1924 in London University but was cancelled by a dissolution of Parliament on 9 October. In 2017 the Manchester Gorton by-election, 2017 was cancelled by a Motion in the House of Commons following the calling of the United Kingdom general election, 2017.
Seats Left Vacant
Occasionally seats are left vacant for a substantial period.
No by-election writ was moved for any seat held by Sinn Féin after the 1918 general election. Four Sinn Féin candidates were elected in two different seats and would have had to decline one of them if they had wanted to take their seats. They were Éamon de Valera (East Clare and East Mayo), Arthur Griffith (East Cavan and North West Tyrone), Eoin MacNeill (Londonderry City and National University of Ireland) and Liam Mellowes (East Galway and North Meath).
By the end of the Parliament, the following Sinn Féin MPs had died without being replaced: Pierce McCan (East Tipperary) of influenza on 6 March 1919, Terence MacSwiney (Mid Cork) following a hunger strike in Brixton prison on 25 October 1920, Frank Lawless (North County Dublin) as a result of a riding injury on 16 April 1922, Joseph McGuinness (Longford) on 31 May 1922, Cathal Brugha (Waterford) in action during the Irish Civil War on 7 July 1922, Harry Boland (South Roscommon) shot while being arrested on 2 August 1922, Arthur Griffith (East Cavan and North West Tyrone) on 12 August 1922, and Michael Collins (South Cork assassinated on 22 August 1922). In each case their seats were abolished in 1922 as a result of the establishment of the Irish Free State.
Other than these cases the longest time a seat has been left vacant with no by-election held is when Dennis Vosper was elevated to the Peerage on 20 April 1964, and no writ was moved by the time Parliament was dissolved on 25 September 1964.
Causes of by-elections
By-elections prompted by assassination
- Batley and Spen by-election, 2016: Jo Cox was killed by a white nationalist while holding a constituency surgery, 16 June 2016
- Eastbourne by-election, 1990: Ian Gow was killed by a Provisional IRA bomb under his car, 30 July 1990
- Enfield Southgate by-election, 1984: Sir Anthony Berry was killed in the Provisional IRA Brighton hotel bombing, 12 October 1984.
- Belfast South by-election, 1982: Rev. Robert Bradford was shot at a constituency surgery by the Provisional IRA, 14 November 1981.
- North Down by-election, July 1922: Field Marshal Sir Henry Wilson, Bt. was shot by the IRA outside his home, 22 June 1922.
By-elections prompted by accidental death
- Heywood and Middleton by-election, 2014: Jim Dobbin died from alcohol poisoning.
- Romsey by-election, 2000: Michael Colvin was killed by a house fire.
- Eastleigh by-election, 1994: Stephen Milligan accidentally choked himself while attempting autoerotic asphyxia.
- Bradford South by-election, 1994: Bob Cryer was killed in a car crash.
- Truro by-election, 1987: David Penhaligon was killed in a car crash.
- Glasgow Central by-election, 1980: Thomas McMillan died from injuries received in falling from a bus.
- Rotherham by-election, 1963: Jack Jones was killed in a car crash.
- South West Norfolk by-election, 1959: Sidney Dye was killed in a car crash.
- Islington North by-election, 1958: Wilfred Fienburgh was killed in a car crash.
- Ipswich by-election, 1957: Richard Stokes died from injuries received in a car crash.
- North Down by-election, 1953: Sir Walter Smiles was killed in the MV Princess Victoria disaster during the storm surge.
- Dundee East by-election, 1952: Thomas Cook was killed in a car crash.
- Edmonton by-election, 1948: Evan Durbin was drowned while swimming.
- Stirling and Falkirk by-election, 1948: Joseph Westwood was killed in a car crash.
- Armagh by-election, 1948: Sir William Allen died from injuries received in a road accident.
- Liverpool Edge Hill by-election, 1947: Dr Richard Clitherow died due to an overdose of barbiturates after he had been "run down and jaded".
- Jarrow by-election, 1947: Ellen Wilkinson was killed by an accidental overdose of medication.
- Glasgow Cathcart by-election, 1946: Francis Beattie was killed in a car crash.
- Smethwick by-election, 1945: Alfred Dobbs was killed in a car crash.
- Motherwell by-election, 1945: James Walker was killed in a road accident.
- Bury St Edmunds by-election, 1944: Lieut-Col. Frank Heilgers was killed in a train crash.
- Manchester Clayton by-election, 1942: John Jagger was killed in a motorcycle accident.
- Stretford by-election, 1939: Anthony Crossley was killed in an air crash.
- Hitchin by-election, 1933: Viscount Knebworth was killed in a plane crash.
By-elections prompted by suicide
- Paisley South by-election, 1997: Gordon McMaster committed suicide.
- Mid Staffordshire by-election, 1990: John Heddle committed suicide.
- Birmingham Northfield by-election, 1982: Jocelyn Cadbury committed suicide.
- Fermanagh and South Tyrone by-election, August 1981: Bobby Sands continued his hunger strike until death.
- Acton by-election, 1968: Bernard Floud committed suicide.
- Harrow West by-election, 1960: Sir Albert Braithwaite committed suicide.
- Leeds West by-election, 1949: Thomas Stamford committed suicide.
- Heywood and Radcliffe by-election, 1946: John Whittaker committed suicide.
- City of Chester by-election, 1940: Sir Charles Cayzer committed suicide after killing his butler.
- Wells by-election, 1939: Anthony Muirhead committed suicide.
- Eastbourne by-election, 1932: Edward Marjoribanks committed suicide.
By-elections prompted by posthumous election of MP
- Bromley by-election, 1945: Sir Edward Taswell Campbell died before his election declaration at the 1945 General Election.
- Monmouth by-election, 1945: Leslie Pym died before his election declaration at the 1945 General Election.
- Combined Scottish Universities by-election, 1935: Noel Skelton died before his election declaration at the 1935 General Election.
- North Galway by-election, 1906: Thomas Higgins died before his election declaration at the 1906 General Election.
By-elections prompted by scandal
- Newark by-election, 2014: Patrick Mercer resigned after being suspended from the House of Commons for six months by the Parliamentary Standards Committee for asking parliamentary questions in exchange for money.
- Eastleigh by-election, 2013: Chris Huhne resigned after pleading guilty to perverting the course of justice in relation to persuading his wife to accept motoring penalty points in 2003.
- Rotherham by-election, 2012: Denis MacShane resigned after House of Commons Standards and Privileges Committee recommended he be suspended from the service of the House for twelve months; their inquiry arose from the United Kingdom Parliamentary expenses scandal.
- Barnsley Central by-election, 2011: Eric Illsley resigned after pleading guilty to charges of false accounting arising from the United Kingdom Parliamentary expenses scandal.
- Glasgow North East by-election, 2009: Michael Martin resigned as Speaker rather than face a vote of no-confidence, amid criticism of his actions arising from the United Kingdom Parliamentary expenses scandal.
- Norwich North by-election, 2009: Ian Gibson resigned after being debarred as a Labour candidate, due to allegations arising from the United Kingdom Parliamentary expenses scandal.
- Beckenham by-election, 1997: Piers Merchant resigned after a newspaper story revealed that his previous denials of an affair were lies.
- Bournemouth East by-election, 1977: John Cordle resigned after he was criticised by a Select Committee for business links to corrupt architect John Poulson.
- Walsall North by-election, 1976: John Stonehouse resigned after being convicted of insurance fraud.
- Berwick-upon-Tweed by-election, 1973: Antony Lambton resigned after his visits to prostitutes and use of cannabis were exposed by the News of the World.
- Stratford-upon-Avon by-election, 1963: John Profumo resigned after his denials of an affair with Christine Keeler were shown to be lies.
- Harrow East by-election, 1959: Ian Harvey resigned after conviction for gross indecency with a guardsman in Hyde Park.
- Paddington North by-election, 1953: Bill Field resigned after conviction for importuning for immoral purposes in a public lavatory.
- Sowerby by-election, 1949: John Belcher resigned after being found to have accepted gifts from businessmen for political favours.
- Scarborough and Whitby by-election, 1941: Sir Paul Latham resigned after he was arrested to be tried by court-martial on 13 charges of disgraceful conduct.
- Derby by-election, 1936: James Henry Thomas resigned after being found to have disclosed budget secrets.
- Balham and Tooting by-election, 1936: Sir Alfred Butt resigned after being found to have disclosed budget secrets.
- Pontypridd by-election, 1931: Thomas Mardy Jones resigned after being found to have abused a travel voucher.
- Buckrose by-election, 1926: Guy Gaunt resigned after being cited as co-respondent in a divorce case.
By-elections prompted to provide seat for seat-less personality
- Nuneaton by-election, 1965: For Frank Cousins.
- Leyton by-election, 1965: For Patrick Gordon-Walker (defeated).
- Sheffield Neepsend by-election, 1950: For Frank Soskice.
- Southampton by-election, 1940: For Sir John Reith.
- Wandsworth Central by-election, 1940: For Ernest Bevin.
- Portsmouth South by-election, 1922: For Leslie Orme Wilson.
- City of London by-election, February 1906: For Arthur Balfour.
- Montrose Burghs by-election, 1896: For John Morley.
By-elections prompted by party splits or disputes
- Sleaford and North Hykeham by-election, 2016: Stephen Phillips resigned, citing irreconcilable differences with his party. Owing to a "lurch to the right", he could no longer accept the appellation "Conservative" or continue to represent his constituents.
- Bermondsey by-election, 1983: Robert Mellish, disenchanted with the left-wing takeover of his Constituency Labour Party (CLP), obtained a job with the London Docklands Development Corporation, left the Labour Party and then resigned to force a byelection.
- Lincoln by-election, 1973: Dick Taverne sought re-election as an Independent 'Democratic Labour' candidate after being deselected by his CLP; he was successful.
- Southwark by-election, 1972: Ray Gunter resigned from the Labour Party in disagreement with its stance opposing European Economic Community entry, and then from Parliament because he had been elected as a Labour candidate.
- Liverpool Garston by-election, 1957: Victor Raikes resigned the Conservative whip over the withdrawal from Suez, and then resigned from Parliament on obtaining a business appointment in Southern Rhodesia.
- Wednesbury by-election, 1957: Stanley Evans, a Labour MP who supported the Conservative government's Suez policy, resigned after being asked to by his Constituency Labour Party.
- Melton by-election, 1956: Anthony Nutting resigned in protest at government policy on Suez.
By-elections resulting from Members seeking re-election over a single issue
- Richmond Park by-election, 2016: Zac Goldsmith resigned to force a by-election on the issue of the expansion of Heathrow Airport, and contested as an Independent. He was defeated by Sarah Olney of the Liberal Democrats
- Haltemprice and Howden by-election, 2008: David Davis resigned to force a by-election on the issue of civil liberties. He was re-elected with neither of the other main parties contesting the seat.
- Northern Ireland by-elections, 1986: Fifteen Unionist MPs resigned and re-contested their seats in protest at the Anglo-Irish Agreement, all but one successful in gaining re-election.
- Kinross-shire and Perthshire by-election, 1938: The Duchess of Atholl resigned in protest at Neville Chamberlain's appeasement policy and sought re-election. She was defeated.
- Southwark North by-election, 1927: Leslie Haden-Guest resigned from the Labour Party over its policy on China, and re-contested the seat as an Independent Constitutionalist with Conservative support. He was defeated, finishing bottom of the poll. The Liberals gained the seat.
- Cork City by-election, 1914: William O'Brien resigned to submit himself to the voters after the Irish Nationalists had made council gains in Cork. He was returned unopposed.
- Bow and Bromley by-election, 1912: George Lansbury resigned to contest his seat on the issue of Women's Suffrage, although he was disenchanted with a range of Labour party policies. He was defeated.
- Stratford-on-Avon by-election, 1909: Thomas Kincaid-Smith resigned from the Liberal Party on the issue of compulsory national service. He stood as an Independent with National Service League support. He was defeated, finishing bottom of the poll.
- Mid Cork by-election, 1906: D. D. Sheehan resigned and re-contested his seat following his expulsion from the Irish Nationalist group for not signing the party pledge. Re-elected as an independent.
By-elections to ratify a change of party
By-elections are ostensibly to vote for a 'person', not a 'party', meaning that a member switching parties mid-term is not cause for a by-election. However, some members do seek re-election under their new party as a point of principle.
- Rochester and Strood by-election, 2014: Mark Reckless resigned and successfully re-contested his seat having left the Conservative Party and joined UKIP.
- Clacton by-election, 2014: Douglas Carswell resigned and successfully re-contested his seat having left the Conservative Party and joined UKIP.
- Merton, Mitcham and Morden by-election, 1982: Bruce Douglas-Mann honoured a pledge to seek re-election when he left Labour to join the SDP. He was defeated by the Conservative candidate.
- Lincoln by-election, 1973: Dick Taverne resigned and successfully re-contested his seat following his resignation from the Labour Party.
- Preston by-election, 1929: William Allen Jowitt resigned and successfully re-contested his seat having left the Liberal Party and joined Labour.
- Kingston-upon-Hull Central by-election, 1926: Joseph Kenworthy resigned and successfully re-contested his seat having left the Liberal Party and joined Labour.
- Isle of Wight by-election, 1904: J. E. B. Seely resigned and was returned unopposed as an Independent Conservative having left the Conservative Party. He joined the Liberals the following month.
- Orkney and Shetland by-election, 1902: Cathcart Wason resigned and successfully recontested his seat having left the Liberal Party.
By-elections triggered when member leaves on principle
- Bristol South East by-election, 1963: Malcolm St Clair honoured a pledge to stand down if law changed to allow Tony Benn to disclaim his peerage.
- Edinburgh Leith by-election, 1927: William Wedgwood Benn resigned following his resignation from the Liberal party and joining the Labour Party. He did not contest the by-election out of fairness to the existing Labour candidate. The seat was narrowly held by a new Liberal candidate.
By-elections prompted by Member's desire to contest another seat
- East Tyrone by-election, 1918: William Redmond resigned in order to defend his late father's seat at Waterford City. He was successful.
- East Worcestershire by-election, 1914: Austen Chamberlain resigned in order to defend his late father's seat at Birmingham West. He was successful.
- East Wicklow by-election, 1911: John Muldoon resigned in order to contest the East Cork by-election. He was successful.
By-elections caused by the previous result being declared void
- Oldham East and Saddleworth by-election, 2011: The result of the 2010 general election was declared void because the victor was found guilty of knowingly making false statements about a rival candidate.
- Winchester by-election, 1997: The result of the 1997 general election was declared void because ballot papers which had not received the official mark would have affected the result, if counted. Liberal Democrat Mark Oaten massively increased the minute majority he had achieved in the general election.
- Oxford by-election, 1924: The result of the 1923 general election was declared void because there were irregularities in the election expenses of the successful candidate.
- Berwick-upon-Tweed by-election, 1923: The result of the 1922 general election was declared void because there were irregularities in the election expenses of the successful candidate.
- North Louth by-election, 1911: The result of the December 1910 general election was declared void because of corrupt practices and bribery on the part of the successful candidate.
By-elections prompted by disqualification of the sitting Member
- Bristol South East by-election, 1961: Tony Benn had inherited a Peerage from his father. Although by-elections were routinely called where Members had succeeded to the Peerage, the seat was not considered vacated until the Member had received a Writ of Summons to the House of Lords, and Benn, who refused to accept the Peerage, did not apply for one. The seat was declared vacant by a resolution of the House of Commons.
- Mid Ulster by-election, 1956: Charles Beattie was found to be disqualified through membership of National Assistance panels. A bill indemnifying him from the consequences of acting as an MP while disqualified was passed by the House of Commons; Beattie did not stand in the by-election.
- Mid Ulster by-election, 1955: Tom Mitchell was disqualified as a felon (resolution of the House).
- Belfast West by-election, 1950: Rev James Godfrey MacManaway was found by the Judicial Committee of the Privy Council to be disqualified, as a Minister of the Church of Ireland.
- Walsall by-election, 1925: William Preston was found to be disqualified owing to his holding government contracts. A bill indemnifying him was passed by the House of Commons and Preston was re-elected at the by-election.
- Dover by-election, 1924: John Astor was disqualified for voting before he took the oath. He was returned unopposed at the by-election.
- Whitechapel by-election, 1913: Sir Stuart Samuel was found to be disqualified owing to his holding government contracts. A bill indemnifying him was passed by the House of Commons and Samuel was narrowly re-elected at the by-election.
- City of London by-election, 1904: Alban Gibbs was found to be disqualified owing to his holding government contracts. Gibbs resigned and was re-elected unopposed at the by-election.
- St. Albans by-election, 1904: Vicary Gibbs was found to be disqualified owing to his holding government contracts. Gibbs resigned and was narrowly defeated at the by-election.
By-elections prompted by expulsion from the House
- South Norfolk by-election, 1955: Peter Baker was expelled after being convicted of uttering forged documents.
- Gravesend by-election, 1947: Garry Allighan was expelled after being found to be in extreme contempt of the House by his peers.
- Hackney South by-election, 1922: Horatio Bottomley was expelled after being convicted of fraud, perjury and false accounting.
- Galway Borough by-election, 1903: the seat was declared vacant after Arthur Alfred Lynch was convicted of high treason.
By-elections prompted by lunacy
By-elections prompted by bankruptcy
- Ashton-under-Lyne by-election, 1928: Cornelius Homan lost his seat after being declared bankrupt.
- Camberwell North by-election, 1922: Henry Newton Knights lost his seat after being declared bankrupt.
- North Galway by-election, 1914: Richard Hazleton resigned before being declared bankrupt. He discharged his bankruptcy and was returned in the by-election.
- Hackney South by-election, 1912: Horatio Bottomley resigned after filing a bankruptcy petition.
- South Kilkenny by-election, 1909: Nicholas Joseph Murphy was declared bankrupt.
By-elections prompted for miscellaneous reasons
- Widnes by-election, 1916: William Hall Walker resigned to permit him to donate his thoroughbred racing stock to create a National Stud in an "arms-length" transaction. He was returned unopposed at the by-election.
By-elections prompted by death of member on wartime active service
Second World War
- Chelmsford by-election, 1945: John Macnamara was killed in action fighting in Italy.
- Berwick-upon-Tweed by-election, 1944: George Charles Grey was killed in action fighting in Normandy, France.
- Bury St Edmunds by-election, 1944: Frank Heilgers was killed in a train crash in Ilford.
- Acton by-election, 1943: Hubert Duggan died of tuberculosis contracted on active service. a
- Darwen by-election, 1943: Stuart Russell died of fever on active service in Egypt.
- Chippenham by-election, 1943: Victor Cazalet was killed in a plane crash in Gibraltar while escorting General Sikorski.
- Birmingham Aston by-election, 1943: Edward Orlando Kellett was killed in action fighting in North Africa.
- Buckingham by-election, 1943: John Whiteley was killed in a plane crash in Gibraltar while escorting General Sikorski.
- Bristol Central by-election, 1943: Lord Apsley was killed in action in a plane crash in the Middle-East.
- King's Lynn by-election, 1943: Somerset Maxwell died of wounds received at the Battle of El Alamein.
- Salisbury by-election, 1942: James Despencer-Robertson died suddenly, apparently from overwork as military secretary at Southern Command Headquarters. b
- Llandaff and Barry by-election, 1942: Patrick Munro died while taking part in an exercise for the Home Guard at Westminster.
- The Wrekin by-election, 1941: James Baldwin-Webb drowned when the SS City of Benares was torpedoed.
- Dudley by-election, 1941: Dudley Joel was killed in action while serving with the Royal Navy.
- Bodmin by-election, 1941: John Rathbone was killed in action on bombing operations over Germany.
- Hitchin by-election, 1941: Sir Arnold Wilson was killed in action over northern France while a gunner in Bomber Command
- King's Norton by-election, 1941: Ronald Cartland was killed in action during the retreat to Dunkirk.
- Manchester Exchange by-election, 1940: Peter Eckersley was killed in action in a plane crash while serving with the Fleet Air Arm.
- Heywood and Radcliffe by-election, 1940: Richard Porritt was killed in action fighting in Belgium.
- Wells by-election, 1939: Anthony Muirhead committed suicide owing to his fear that a leg-injury might prevent his service in the War. b
- Notes: The above list is of those members either mentioned as having died on War Service in a written Commons answer from Prime Minister Winston Churchill on 19 January 1945, or who appear in the House of Commons Book of Remembrance unveiled in 1949.
- a Mentioned in the written Commons answer, but does not appear in the House of Commons Book of Remembrance.
- b Not mentioned in the written Commons answer, but does appear in the House of Commons Book of Remembrance.
- NB:- The above list does not include the names of three members whose deaths on active service were overtaken by the 1945 General Election. For a complete list see Records of members of parliament of the United Kingdom#Second World War
First World War
- Prestwich by-election, October 1918: Oswald Cawley had been killed in action in France.
- Bath by-election, 1918: Lord Alexander Thynne had been killed in action in France.
- Canterbury by-election, 1918: Francis Bennett-Goldney had been killed by an on-duty car accident in France.
- Ross by-election, 1918: Percy Clive had been killed in action in France.
- Manchester South by-election, 1918: Philip Glazebrook had been killed in action in Palestine.
- Wisbech by-election, 1917: The Hon Neil Primrose died of wounds received in Palestine.
- Spalding by-election, 1917: The Hon Francis McLaren had been killed in a flying accident serving with the Royal Flying Corps.
- East Clare by-election, 1917: Willie Redmond had been killed in action in Belgium.
- Henley by-election, 1917: Valentine Fleming had been killed in an air raid in France.
- North Ayrshire by-election, 1916: Duncan Frederick Campbell had died in England of wounds received from a landmine on the Western Front.
- Winchester by-election, 1916: The Hon Guy Baring had been killed in the Battle of the Somme in France.
- Tewkesbury by-election, 1916: Michael Hicks Beach, Viscount Quenington had died of wounds in Egypt.
- St Austell by-election, 1915: The Hon Thomas Agar-Robartes had died of wounds received in the Battle of Loos in France.
- Cardiff by-election, 1915: Lord Ninian Crichton-Stuart had been killed in action in France.
- Uxbridge by-election, 1915: The Hon Charles Thomas Mills had been killed in action in France.
- Heywood by-election, 1915: Harold Thomas Cawley had been killed in action in the Battle of Gallipoli.
- Kilmarnock Burghs by-election, 1915: William Glynne Charles Gladstone had been killed in action in France.
- Mid Antrim by-election, 1915: The Hon Arthur O'Neill had been killed in action in the Ypres Salient in Belgium.
Incumbents fall directly from first place to third place
- Littleborough and Saddleworth by-election, 1995 Conservatives loss, gained by the Liberal Democrats
- Perth and Kinross by-election, 1995 Conservative loss, gained by the SNP
- Eastleigh by-election, 1994 Conservative loss, gained by the Liberal Democrats
- Brecon and Radnor by-election, 1985 Conservative loss, gained by the Liberals
- Mitcham and Morden by-election, 19821 Labour loss, gained by the Conservatives
- Rochdale by-election, 1958 Conservative loss, gained by Labour
- Merthyr by-election, 1934 ILP loss, gained by Labour
- Holland with Boston by-election, 1929 Conservative loss, gained by the Liberals
- Bosworth by-election, 1927 Conservative loss, gained by the Liberals
- Hull Central by-election, 19262 Liberal loss, gained by Labour
- South Norfolk by-election, 1920 Liberal loss, gained by Labour
- 1 Bruce Douglas-Mann had been re-elected as Labour MP for the seat in the 1979 General Election. In 1981, along with several other MPs, he defected to the newly formed Social Democratic Party. Against his new colleagues' advice, he honoured a pledge to face his electors under his new party colours and precipitated a by-election. He came second in the by-election which was won by the Conservatives. The new Labour candidate finished third.
- 2 the Liberal MP, Lt-Commander the Hon. Joseph Montague Kenworthy, defected to Labour and sought re-election under his new colours. He was successful, and the new Liberal candidate lost his deposit.
Incumbent Government gains seats
These records show the rare occasions when the Government won a seat they had not won at the previous General election.
- Copeland by-election, 2017, from Labour
- Mitcham and Morden by-election, 1982, from Labour
- Bristol South-East by-election, 19611, from Labour
- Brighouse and Spenborough by-election, 1960, from Labour
- Sunderland South by-election, 1953, from Labour
- Combined English Universities by-election, 1926, from the Liberals
- Hackney South by-election, 1922, from the Independent Parliamentary Group
- Woolwich East by-election, 1921, from Labour
- Stockport by-election, 1920, from Coalition Labour2
- 1 Seat awarded by Election Court to Conservative runner-up because Labour victor deemed ineligible.
- 2 An arguable gain; Stockport was a two-member seat; in the 1918 general election it was won by two supporters of the Coalition Government, one a Liberal and one a Labour member. After a death and a resignation, a by-election was held for both seats. The seats were again won by two Coalition Government supporters, but this time a Conservative and a Liberal, while a Labour candidate who did not support the government was unsuccessful.
- Liverpool Scotland by-election, 19291, from Irish Nationalist
- Preston by-election, 19292, from the Liberals
- Liverpool West Toxteth by-election, 1924, from the Conservatives
- 1 Uncontested gain from Irish Nationalist.
- 2 Liberal MP defected to Labour and was re-elected as Labour at a by-election the Liberals did not contest.
Labour won both the West Bromwich West by-election, 2000 and Glasgow North East by-election, 2009, regarded as a gain from the contest at the United Kingdom general elections in 1997 and 2005 respectively as those seats had been contested by the then Speakers of the House of Commons, although prior to assuming the Speakership they had both been elected as Labour MPs in safe seats.
- Hanley by-election, 1912, from Labour
Principal Opposition loses seats
These records show the rare occasions when the official Opposition failed to hold on to a seat they had won at the previous General election.
- Romsey by-election, 2000, lost to the Liberal Democrats
- Mid Ulster by-election, 1969, (from Ulster Unionist), lost to Unity
- Roxburgh, Selkirk and Peebles by-election, 1965, lost to the Liberals
- Paddington South by-election, 19301, lost to the Empire Free Trade Crusade
- Liverpool West Toxteth by-election, 1924, lost to Labour
- 1A confused situation, where the victorious Empire Free Trade Crusade candidate was effectively a right-wing unofficial Conservative, who subsequently took the whip and was re-elected as official Conservative candidate.
- Copeland by-election, 2017, lost to the Conservatives
- Bradford West by-election, 2012, lost to Respect
- Glasgow Govan by-election, 1988, lost to the SNP
- Greenwich by-election, 1987, lost to the SDP
- Bermondsey by-election, 1983, lost to the Liberals
- Mitcham and Morden by-election, 1982, lost to the Conservatives
- Glasgow Govan by-election, 1973, lost to the SNP
- Lincoln by-election, 1973, lost to Lincoln Democratic Labour
- Rochdale by-election, 1972, lost to the Liberals
- Bristol South-East by-election, 19611, awarded to the Conservatives
- Brighouse and Spenborough by-election, 1960, lost to the Conservatives
- Sunderland South by-election, 1953, lost to the Conservatives
- Southwark North by-election, 1927, lost to the Liberals
- Anglesey by-election, 19232, lost to the Liberals
- Woolwich East by-election, 1921, lost to the Coalition Conservatives
- 1seat awarded by Election Court to Conservative runner-up because Labour victor Viscount Stansgate was deemed ineligible.
- 2Sir Owen Thomas had been elected as Independent Labour, took the whip for a while, before reverting to Independent Labour.
By-election holds overturned at next general election
By-elections usually see the high-water mark of any challenge to the incumbents. On rare occasions a party has failed to overturn an incumbent in the by-election yet has gone on to gain the seat at the subsequent general election.
- Eastleigh by-election, 2013, held by the Liberal Democrats; gained by the Conservatives in 2015.
- Inverclyde by-election, 2011, held by Labour; gained by the Scottish National Party in 2015.
- Blaenau Gwent by-election, 2006, held by an independent; gained by Labour in 2010.
- South Down by-election, 1986, held by the Ulster Unionists; gained by the Social Democratic and Labour Party in 1987.
- Darlington by-election, 1983, held by Labour; gained by the Conservatives in 1983.
- Dundee East by-election, 1973, held by Labour; gained by the Scottish National Party in February 1974.
- Bolton East by-election, 1960, held by the Conservatives; gained by Labour in 1964.
- Carmarthen by-election, 1928, held by the Liberals; gained by Labour in 1929.
- New Forest by-election, 1905, held by the Conservatives; gained by the Liberals in 1906.
By-election victors had not contested previous general election
It is unusual for a political party which has not contested a seat at a general election to take it at a subsequent by-election. Many of the parties which have done so were founded after the general election. Independent candidates are not included.
- Rochester and Strood by-election, 2014, gained by UKIP
- Clacton by-election, 2014, gained by UKIP
- South Antrim by-election, 2000, gained by the DUP
- North Down by-election, 1995, gained by the UK Unionists
- Glasgow Hillhead by-election, 1982, gained by the SDP 1
- Crosby by-election, 1981, gained by the SDP 1
- Isle of Ely by-election, 1973, gained by the Liberals
- Lincoln by-election, 1973, gained by Lincoln Democratic Labour 2
- Mid Ulster by-election, 1969, gained by Unity
- Hamilton by-election, 1967, gained by the SNP
- Torrington by-election, 1958, gained by the Liberals
- Chelmsford by-election, 1945, gained by Common Wealth
- Motherwell by-election, 1945, gained by the SNP
- Skipton by-election, 1944, gained by Common Wealth
- Eddisbury by-election, 1943, gained by Common Wealth
- Belfast West by-election, 1943, gained by the Northern Ireland Labour Party
- Ross and Cromarty by-election, 1936, gained by National Labour
- Combined Scottish Universities by-election, 1936, gained by National Labour
- Merthyr by-election, 1934, gained by Labour
- Paddington South by-election, 1930, gained by Empire Free Trade Crusade
- Liverpool Scotland by-election, 1929, gained by Labour
- Kingston-upon-Hull Central by-election, 1929, gained by Labour
- Kirkcaldy by-election, 1921, gained by Labour
- Woolwich East by-election, 1921, gained by the Coalition Conservatives
- 1 Alliance partner the Liberal party had contested the seat.
- 2 the victor was the sitting MP, who had left the Labour party.
Victory from third or lower place
- Bradford West by-election, 2012, gained by Respect, from fifth place
- Leicester South by-election, 2004, gained by the Liberal Democrats, from third place
- Brent East by-election, 2003, gained by the Liberal Democrats, from third place
- Glasgow Govan by-election, 1988, gained by the SNP, from fourth place
- Greenwich by-election, 1987, gained by the SDP, from third place
- Brecon and Radnor by-election, 1985, gained by the Liberals, from third place
- Bermondsey by-election, 1983, gained by the Liberals, from third place
- Croydon North West by-election, 1981, gained by the Liberals, from third place
- Glasgow Govan by-election, 1973, gained by the SNP, from third place
- Berwick-upon-Tweed by-election, 1973, gained by the Liberals, from third place
- Ripon by-election, 1973, gained by the Liberals, from third place
- Sutton and Cheam by-election, 1972, gained by the Liberals, from third place
- Carmarthen by-election, 1966, gained by Plaid Cymru, from third place
- Orpington by-election, 1962, gained by the Liberals, from third place
- Holland with Boston by-election, 1929, gained by the Liberals, from third place
Incumbent party did not contest
- Richmond Park by-election, 2016 (incumbent Conservative MP ran as an Independent with party backing)
- North Down by-election, 1995 (party disintegrated before by-election)
- Bristol South East by-election, 1963 (Conservative candidate awarded seat after 1961 by-election had agreed to stand aside, if law changed to permit disqualified Labour candidate to take his seat)
- Cardiff East by-election, 1942 (Conservatives stood aside to allow election of National Government minister)
- City of London by-election, 1940 (Conservatives stood aside to allow election of National Government minister)
- Southampton by-election, 1940 (National Liberals stood aside to allow election of National Government minister)
- Combined Scottish Universities by-election, 1938 (National Labour stood aside to allow election of National Government minister)
- Ross and Cromarty by-election, 1936 (National Liberals stood aside to allow election of National Government minister from National Labour)
- Combined Scottish Universities by-election, 1936 (Conservatives stood aside to allow election of National Government minister from National Labour)
- Perth by-election, 1935 (Conservatives stood aside to allow election of National Liberal)
- Liverpool Scotland by-election, 1929 (lone mainland Irish Nationalist was essentially a Labour supporter)
- Preston by-election, 1929 (Liberals acquiesced to William Jowitt becoming Labour's Attorney General)
Losers had been unopposed at previous election
- Paddington South by-election, 1930 Conservative loss, gained by Empire Free Trade Crusade.
- Liverpool Scotland by-election, 1929 Irish Nationalist loss, gained by Labour.1
- Halifax by-election, 1928 Speaker loss, gained by Labour.2
- Kirkcaldy Burghs by-election, 1921 Coalition Liberal loss, gained by Labour.
- Woolwich East by-election, 1921 Labour loss, gained by Conservative.
- The Wrekin by-election, February 1920 Coalition Liberal loss, gained by Independent.
- 1 the Nationalists did not contest the by-election
- 2 the Speaker had originally been a Liberal MP.
Major party did not run
The Conservatives, Liberal Democrats, UKIP, and Green Party declined to run candidates in the Batley and Spen by-election, 2016, due to the circumstances regarding the killing of the previous MP, Jo Cox.
Neither the Liberal Democrat nor the Labour Party stood candidates in the Haltemprice and Howden by-election, 2008. The by-election was a single-issue election in regards to government security policy, in which the Liberal Democrats supported the Conservative candidate.
Prior to 2008, the last by-election without an official Liberal Democrat, Liberal or SDP candidate had been the Newham North East by-election, 1994; the Lib Dems nominated a candidate, but he joined the Labour Party before the election. No official Liberal candidate was nominated for the Glasgow Central by-election, 1980, whilst no Liberal stood in either the Westhoughton by-election, 1973 or the West Bromwich by-election, 1973, both held on 24 May 1973.
The more fluid nature of politics in Northern Ireland makes it harder to define all major parties. In addition many by-elections have not been contested by parties holding other seats in the House of Commons, whether due to agreements with other parties, poor organisation in the constituency or the particular circumstances on the by-election. However, for the period since 1981 (which saw the first by-elections in twelve years, during which time several major political realignments had occurred) the main parties are usually considered to be the Democratic Unionist Party, Sinn Féin, the Social Democratic and Labour Party (SDLP) and the Ulster Unionist Party.
At the Mid Ulster by-election, 2013. a single "unity" candidate was backed by the withdrawal of the Democratic Unionist Party, Ulster Conservatives and Unionists and Traditional Unionist Voice. Prior to Mid Ulster in 2013, the most recent examples of by-elections without official Democratic Unionist candidates were the North Down by-election, 1995 and the Upper Bann by-election, 1990. They also did not stand in the twelve seats held by other Unionist parties in the 15 by-elections in 1986.
The last by-election without official candidates from either Sinn Féin or the SDLP was the North Down by-election, 1995. Both parties also declined to stand in the eleven Unionist majority seats in the 15 by-elections in 1986. The SDLP also did not contest either the April or August 1981 by-elections in Fermanagh and South Tyrone.
The last by-elections without official Ulster Unionist candidates prior to Mid Ulster in 2013 were North Antrim, East Belfast, Mid Ulster and North Down in the 15 by-elections in 1986.
The main British parties have generally not stood in seats in Northern Ireland. The by-election exceptions are the Upper Bann by-election, 1990 (Conservatives and continuing SDP) and the North Down by-election, 1995 (Conservatives). Prior to the 1970s the Ulster Unionists were effectively the local Conservatives, whilst the Liberals contested some but not all seats. The SDLP has traditionally seen itself as a "sister party" to the British Labour party, and its MPs usually accept the Labour whip in Parliament.
Victories by minor parties
Victories by independent and minor party candidates since 1945. For a complete list, see the list of UK minor party and independent MPs elected.
- Rochester and Strood by-election, 2014 - UKIP win second elected MP victory following Clacton result.
- Clacton by-election, 2014 - UKIP win first elected MP victory following numerous second places in by-elections.
- Bradford West by-election, 2012 - Respect candidate George Galloway delivers the party's first by-election gain.
- Blaenau Gwent by-election, 2006 - Independent candidate, election agent of the previous incumbent, won with 46.7%.
- North Down by-election, 1995 - UK Unionist Party candidate won with tacit backing of Democratic Unionist Party
- North Down by-election, 1986 - Ulster Popular Unionist Party candidate won without Unionist opposition.
- Fermanagh and South Tyrone by-elections, August and April 1981 - Anti H-Block candidates linked to Sinn Féin won.
- Lincoln by-election, 1973 - Lincoln Democratic Labour Association, incumbent MP held seat in new party colours.
- Mid Ulster by-election, 1969 - Unity candidate won without Irish Nationalist opposition.
- Mid Ulster by-election, 1956 - Independent Unionist candidate won without Unionist opposition.
- Glasgow Bridgeton by-election, 1946 - Independent Labour Party candidate held seat.
Minor parties other strong performance
Parties without representation in the House of Commons which saved their deposit:
|Alliance||Belfast East by-election, 1986||Oliver Napier||5,917||17.4||2||Party historically represented at Westminster|
|Alliance||Belfast North by-election, 1986||Paul Maguire||5,072||16.7||2||Party historically represented at Westminster|
|Alliance||Belfast South by-election, 1982||David Cook||11,726||26.9||2||Party historically represented at Westminster|
|Alliance||Belfast South by-election, 1986||David Cook||7,635||25.0||2||Party historically represented at Westminster|
|Alliance||East Antrim by-election, 1986||Sean Neeson||5,405||15.1||2||Party historically represented at Westminster|
|Alliance||North Down by-election, 1986||John Cushnahan||8,066||20.8||2||Party historically represented at Westminster|
|Alliance||North Down by-election, 1995||Oliver Napier||6,970||25.4||3||Party historically represented at Westminster|
|Alliance||South Antrim by-election, 2000||David Ford||2,031||6.6||5||Party represented in the Northern Ireland Assembly and historically at Westminster|
|All Party Alliance||Oldham West by-election, 1968||John Creasey||3,389||13.2||3|
|BNP||Dagenham by-election, 1994||John Tyndall||1,511||7.0||4|
|BNP||Barnsley Central by-election, 2011||Enis Dalton||1,463||6.0||4||Party represented in the European Parliament|
|BNP||Sedgefield by-election, 2007||Andrew Spence||2,494||8.9||4|
|BNP||Rotherham by-election, 2012||Marlene Guest||1,804||8.5||3||Party represented in the European Parliament|
|English Democrat||Haltemprice and Howden by-election, 2008||Joanne Robinson||1,714||7.2||3|
|Green||Haltemprice and Howden by-election, 2008||Shan Oakes||1,758||7.4||2||Party represented in the European Parliament and historically and subsequently at Westminster|
|Green||Norwich North by-election, 2009||Rupert Read||3,350||9.7||5||Party represented in the European Parliament and historically and subsequently at Westminster|
|Green||Vauxhall by-election, 1989||Henry Bewley||1,767||6.1||4||Party historically represented at Westminster|
|Independent||Mid Ulster by-election, 2013||Nigel Lutton||12,781||34.4||2||DUP, UUP and TUV did not stand candidates and supported Lutton's candidacy|
|Independent||Combined English Universities by-election, 1946||Mary Stocks||5,124||28.0||2|
|Independent||Combined English Universities by-election, 1946||Ernest Simon||4,028||22.0||3|
|Independent||East Londonderry by-election, 1986||Peter Barry||2,001||6.1||2||Fictitious paper candidate running as "For the Anglo-Irish Agreement"|
|Independent||South Shields by-election, 2013||Ahmed Khan||1,331||5.4||4|
|Independent||Barnsley Central by-election, 2011||Tony Devoy||1,266||5.2||5|
|Independent||Hamilton South by-election, 1999||Stephen Mungall||1,075||5.5||5|
|Independent||Sedgefield by-election, 2007||Paul Gittins||1,885||6.7||5|
|Independent||South Antrim by-election, 1986||Peter Barry||1,870||5.9||2||Fictitious paper candidate running as "For the Anglo-Irish Agreement"|
|Independent||Strangford by-election, 1986||Peter Barry||1,993||5.8||2||Fictitious paper candidate running as "For the Anglo-Irish Agreement"|
|Independent Labour||Combined English Universities by-election, 1946||S. Wormald||3,414||18.7||4|
|Independent Labour||Liverpool Walton by-election, 1991||Lesley Mahmood||2,613||6.5||3|
|Independent Unionist||Down by-election, 1946||J. Hastings-Little||16,895||17.1||3|
|Independent Unionist||North Down by-election, 1995||Alan Chambers||2,170||7.9||4|
|Anti-Partition||Armagh by-election, 1948||James O'Reilly||16,284||40.3||2||Party later represented at Westminster|
|Irish Labour||Belfast West by-election, 1950||Jack Beattie||30,833||49.2||2||Party previously and later represented at Westminster|
|Lincolnshire Independent||Sleaford and North Hykeham by-election, 2016||Marianne Overton||2,892||8.8||5|
|National Fellowship||Bristol South East by-election, 1963||Edward Martell||4,834||19.0||2|
|National Front||West Bromwich by-election, 1973||Martin Webster||4,789||16.0||3|
|NI Labour||Belfast East by-election, 1959||James Gardner||14,264||42.2||2||Party represented in the Parliament of Northern Ireland and previously at Westminster|
|NI Labour||Belfast South by-election, 1952||Samuel Napier||7,655||24.9||2||Party previously represented at Westminster|
|NI Labour||Belfast South by-election, 1963||Norman Searight||7,209||25.8||2||Party represented in the Parliament of Northern Ireland and previously at Westminster|
|NI Labour||Down by-election, 1946||Desmond Donnelly||28,846||29.3||2||Party represented in the Parliament of Northern Ireland and previously at Westminster|
|Peace||Middlesbrough by-election, 2012||Imdad Hussain||1,060||6.3||5|
|Plaid Cymru||Aberdare by-election, 1946||Wynne Samuel||7,090||20.0||2||Party later represented at Westminster|
|Plaid Cymru||Aberdare by-election, 1954||Gwynfor Evans||5,671||16.0||2||Party later represented at Westminster|
|Plaid Cymru||Merthyr Tydfil by-election, 1972||Emrys Roberts||11,852||37.0||2||Party previously and later represented at Westminster|
|Plaid Cymru||Ogmore by-election, 1946||T. R. Morgan||5,685||29.4||2||Party later represented at Westminster|
|People Before Profit||Belfast West by-election, 2011||Gerry Carroll||1,751||7.6||3||Two members elected to the Dáil in 2011|
|Respect||Birmingham Hodge Hill by-election, 2004||John Rees||1,282||6.3||4||George Galloway MP was a party member, but was usually considered Independent Labour in Parliament at the time|
|Respect||Leicester South by-election, 2004||Yvonne Ridley||3,724||12.7||4||George Galloway MP was a party member, but was usually considered Independent Labour in Parliament at the time|
|SNP||Glasgow Bridgeton by-election, 1946||M. Wood||2,575||13.9||4||Party previously and later represented at Westminster|
|SNP||Glasgow Bridgeton by-election, 1961||Ian MacDonald||3,549||18.7||3||Party previously and later represented at Westminster|
|SNP||Glasgow Pollok by-election, 1967||George Leslie||10,884||29.2||3||Party previously and later represented at Westminster|
|SNP||South Ayrshire by-election, 1970||Sam Purdie||7,785||19.9||3||Party previously and later represented at Westminster|
|SNP||West Lothian by-election, 1962||William Wolfe||9,750||23.3||2||Party previously and later represented at Westminster|
|Scottish Socialist||Falkirk West by-election, 2000||Iain Hunter||989||5.1||4||Party represented in the Scottish Parliament|
|Scottish Socialist||Glasgow Anniesland by-election, 2000||Charlie McCarthy||1,441||7.2||5||Party represented in the Scottish Parliament|
|Scottish Socialist||Hamilton South by-election, 1999||Shareen Blackall||1,847||9.5||3||Party represented in the Scottish Parliament|
|Social Democratic||Neath by-election, 1991||John Warman||1,826||5.3||5||Party of same name which was dissolved in 1990 was represented in Parliament|
|Socialist Alliance||Preston by-election, 2000||Terry Cartwright||1,210||5.7||4|
|Socialist Alliance||Tottenham by-election, 2000||Weyman Bennett||885||5.4||4|
|Socialist Labour||Barnsley East by-election, 1996||Ken Capstick||949||5.3||4|
|Socialist Labour||Hemsworth by-election, 1996||Brenda Nixon||1,193||5.4||4|
|Socialist Labour||Ogmore by-election, 2002||Christopher Herriot||1,152||6.3||5|
|UKIP||Hartlepool by-election, 2004||Stephen Allison||2,347||10.2||3||Party represented in the European Parliament|
|UKIP||Bromley and Chislehurst by-election, 2006||Nigel Farage||2,347||8.1||3||Party represented in the European Parliament|
|UKIP||Norwich North by-election, 2009||Glenn Tingle||4,068||11.8||4||Party represented in the European Parliament|
|UKIP||Oldham East and Saddleworth by-election, 2011||Paul Nuttall||2,029||5.8||4||Party represented in the European Parliament|
|UKIP||Barnsley Central by-election, 2011||Jane Collins||2,953||12.2||2||Party represented in the European Parliament|
|UKIP||Feltham and Heston by-election, 2011||Andrew Charalambous||1,276||5.5||4||Party represented in the European Parliament|
|UKIP||Cardiff South and Penarth by-election, 2012||Simon Zeigler||1,179||6.1||5||Party represented in the European Parliament|
|UKIP||Corby by-election, 2012||Margot Parker||5,108||14.3||3||Party represented in the European Parliament|
|UKIP||Rotherham by-election, 2012||Jane Collins||4,648||21.8||2||Party represented in the European Parliament|
|UKIP||Middlesbrough by-election, 2012||Richard Elvin||1,990||11.8||2||Party represented in the European Parliament|
|UKIP||Croydon North by-election, 2012||Winston McKenzie||1,400||5.7||3||Party represented in the European Parliament|
|UKIP||Eastleigh by-election, 2013||Diane James||11,571||27.8||2||Party represented in the European Parliament|
|UKIP||South Shields by-election, 2013||Richard Elvin||5,988||24.2||2||Party represented in the European Parliament|
|UKIP||Wythenshawe and Sale East by-election, 2014||John Bickley||4,301||18.0||2||Party represented in the European Parliament|
|UKIP||Newark by-election, 2014||Roger Helmer||10,028||25.9||2||Party represented in the European Parliament|
|UKIP||Heywood and Middleton by-election, 2014||John Bickley||11,016||38.7||2||Party represented in the European Parliament, and also represented in the House of Commons following the Clacton by-election the same day.|
|Workers' Party||Belfast North by-election, 1986||Seamus Lynch||3,563||11.8||3|
|Workers' Party||Lagan Valley by-election, 1986||John Lowry||3,328||9.3||2|
|Workers' Party||Upper Bann by-election, 1986||Tom French||6,978||19.2||2|
Miscellaneous notable results
It is unusual for one of the major parties to finish outside of the top three in England and Wales (or outside of the top four in Scotland). It is also unusual for the principal opposition party to suffer a significant reverse in its share of the vote or ranking.
- The Richmond Park by-election, 2016 was the first Liberal Democrat gain since 2010, showing tentative signs of recovery for the party. It also gave them a female MP for the first time in the 56th parliament. In addition it was the first occasion in more than a century of Labour losing their deposit in a London by-election.
- The Clacton by-election, 2014 saw the election of the first UKIP MP on the largest swing ever against the Conservative Party. It was also the first time that a party had gained a seat not having contested the previous election since the Isle of Ely by-election, 1973. The Liberal Democrat's 1.4% of the vote was their worst result in an English seat since 1924.
- The Eastleigh by-election, 2013 delivered several records. It was the first time in an English seat that both Labour and Conservative finished outside of the top two. For the first time, UKIP came close to winning a seat. It was the closest three-cornered English by-election since the Penistone by-election, 1921, and, aside from the Combined English Universities by-election, 1946, it was won with the lowest winning share of the vote since 1918. Aside from the contrived example of the Richmond by-election, 1989 it was also the first time Labour had finished fourth in a by-election while in Opposition.
- At the Rotherham by-election, 2012, the Conservative party fell from second to fifth place (equalling its previous lowest position in a by-election in mainland Britain) while the Liberal Democrats fell from third place to eighth, the lowest ranking ever achieved by a major party in a by-election. This followed the Barnsley Central by-election, 2011, where the Liberal Democrats took sixth place, dropping from second at the 2010 general election. The Rotherham by-election was also the first recorded by-election result to have women in the top four places.
- At the Blaenau Gwent by-election, 2006, held on the same day as Bromley and Chislehurst, the Conservative Party's fifth-place ranking equalled the worst-place achieved by a major party in England or Wales, a feat the Conservatives had first achieved in the same seat in the 2005 General Election. The Blaenau victor, Dai Davies was the first independent to hold a seat previously occupied by an independent since Sir C.V.F. Townshend held The Wrekin in 1920.
- In the Hamilton South by-election, 1999, and Glasgow North East by-election, 2009 the Liberal Democrats came sixth in both cases, equalling the worst ever placing by a major party in the UK. In 1999 the party had 634 votes while in Glasgow the party gained 474 votes.
- At the Walsall North by-election, 1976, the Liberal Party could take only fifth place. Beaten by an independent and a minor party candidate, at the time, this was the worst placing for any major party in an English by-election since at least 1945.
- At the Henley by-election, 2008 the Labour Party finished in fifth place, the worst ranking for the party in its history, and a record low for any government in a UK mainland constituency. The lowest ever for an incumbent government was the Upper Bann by-election, 1990 when the Conservatives came sixth, although they had not previously contested the seat.
- The drop in the Conservative share of the vote, 11.1%, at the Bromley and Chislehurst by-election, 2006 was their worst result in a Conservative-held seat while in opposition since 19301. At the same by-election, the Labour Party's fall from second to fourth place was the first time the party had suffered such a reverse in an English seat.
- The Conservative Party fell from second to fourth place in the Hartlepool by-election, 2004 and fell from third to fourth place in the Liverpool Walton by-election, 1991. At the time their worst ranking in an English by-election since at least 1945 was the drop from third place to fourth place in the Newham South by-election, 1974, whilst the also dropped to fourth place in the Bermondsey by-election, 1983.
- The Labour party fell from second to fourth place in the Ceredigion by-election, 2000.
- At the Bootle by-election, 1990 the "continuing" SDP finished seventh out of eight candidates, behind the Monster Raving Loony Party, in a seat parts of which had once been in adjoining Crosby, scene of the party's greatest triumph only eight years previously.
- The Labour Party achieved fourth place in the Richmond (Yorks) by-election, 1989 although this was contrived somewhat by the Social and Liberal Democrats and Social Democratic Party parties running separate candidates.
- The last time the Liberals lost a by-election they were defending was at the Carmarthen by-election, 1957, defeated by the former Liberal MP turned Labour candidate, Lady Megan Lloyd-George. The Liberal parliamentary contingent was thus reduced to five MPs, its lowest ever level.
Notes 1Excluding the Westminster St George's by-election, 1931 and the Paddington South by-election, 1930, which were essentially intra-Conservative contests, the previous worst result was, ironically, the Bromley by-election, 1930
By-elections having national significance
- Copeland by-election, 2017: A Conservative win in a previously safe Labour seat confirmed the party's strong opinion poll lead and prompted an early election.
- Richmond Park by-election, 2016: After losing most of its seats in the 2015 general election, a Lib Dem gain on a large swing in a strongly Remain seat marked the beginning of a turnaround for the party and demonstrated the political effects of Brexit.
- Clacton by-election, 2014: The first by-election victory for the United Kingdom Independence Party
- Crewe and Nantwich by-election, 2008: A Conservative gain (from Labour in this case) at a by-election for the first time since 1982, and the first time as an opposition party since 1978, demonstrated the Conservatives were back in contention to possibly win the next general election.
- Brent East by-election, 2003: A Lib Dem gain of a Labour safe seat on a 29% swing demonstrated the political effect of public dissatisfaction with the Iraq War.
- Wirral South by-election, 1997: A Labour gain on a large swing just weeks before a general election confirmed the move in the party's favour was real.
- Liverpool Walton by-election, 1991: The Militant group, as Walton Real Labour, opposed a Labour candidate for the first time; their showing led to the decision to re-organise as Militant Labour without using entryist tactics.
- Bootle by-election, May 1990: Abysmal showing of the 'continuing SDP' led to the party being wound up.
- Greenwich by-election, 1987: Defeat of a left-wing Labour candidate demonstrated the party's vulnerability.
- Darlington by-election, 1983: Labour's successful defence of a marginal seat stabilised the party, and secured the position of Leader Michael Foot.
- Crosby by-election, 1981: Victory of the Social Democratic Party in a rock-solid Conservative seat showed the national appeal of the party.
- Fermanagh and South Tyrone by-election, April 1981: Election of Maze prison hunger-striker Bobby Sands demonstrated that nationalist voters could support violent Republican candidates; taken by the Republican movement as a vindication of their stance.
- Birmingham Stechford by-election, 1977: The loss of the seat to the Conservatives tipped Labour under James Callaghan into minority government status, necessitating the Lib-Lab Pact.
- Hamilton by-election, 1967: Scottish National Party victory massively boosted the prospects of the party.
- Hull North by-election, 1966: Easy Labour victory in a marginal seat demonstrated to Prime Minister Harold Wilson that he would probably win a snap general election, and led to the construction of the Humber Bridge.
- Roxburgh, Selkirk and Peebles by-election, 1965: Rare Conservative loss in Opposition leads to resignation of leader Sir Alec Douglas-Home and election of Edward Heath as first democratically elected Conservative leader.
- Leyton by-election, 1965: Foreign Secretary Patrick Gordon-Walker, who was found the seat after losing Smethwick in 1964, is again defeated; he is forced to resign from the Government.
- Kinross and West Perthshire by-election, 1963: Prime Minister Sir Alec Douglas-Home successfully returned to the House of Commons after disclaiming his Peerage.
- Orpington by-election, 1962: A Liberal gain in a suburban seat led to a national revival for the party.
- Bristol South East by-election, 1961: Incumbent Labour MP Tony Benn re-elected after inheriting a Peerage; the seat was awarded to the defeated Conservative, but the circumstances led to the Peerage Act 1963 allowing hereditary Peerages to be disclaimed.
- Oxford by-election, 1938: After a campaign dominated by appeasement and the Munich agreement, the government candidate won.
- Liverpool Wavertree by-election, 1935: Intervention of Independent Conservative Randolph Churchill, on platform of rearmament and Anti-Indian Home Rule, hands safe seat to Labour on largest ever swing (30%). Indication of hostility to National Government, and Prime Minister Ramsay MacDonald resigns within months.
- Fulham East by-election, 1933: Unexpected Labour gain in a previously safe Conservative constituency, ascribed to pacifism.
- Newport by-election, 1922: Election of an anti-Coalition Conservative in a tight three way contest spurred on Conservative MPs to end their coalition with David Lloyd George.
- Dartford by-election, 1920: massive swing to Labour prefigures the party's eclipse of the Liberals.
Firsts and lasts
- Last Conservative gain in a by-election: Copeland by-election, 2017
- Last Labour gain at a by-election: Corby by-election, 2012
- Last Liberal Democrat gain at a by-election: Richmond Park by-election, 2016
- First UK Independence Party gain at a by-election: Clacton by-election, 2014
- Last UK Independence Party gain at a by-election: Rochester and Strood by-election, 2014
- First by-election gain by a Northern Ireland party: Belfast West by-election, 1943 (Northern Ireland Labour Party from Ulster Unionist Party)
- Last by-election gain by a Northern Ireland party: South Antrim by-election, 2000 (Democratic Unionist Party from Ulster Unionist Party)
- First by-election gain by the Social Democratic Party (SDP): Crosby by-election, 1981
- Last by-election gain by the Social Democratic Party (SDP): Greenwich by-election, 1987
- Last by-election gain by the Liberal Party: Ryedale by-election, 1986
- First by-election gain by the Scottish National Party: Motherwell by-election, 1945
- Last by-election gain by the Scottish National Party: Glasgow East by-election, 2008
- First and last by-election gain by Plaid Cymru: Carmarthen by-election, 1966
- Last unopposed by-election in England, Scotland or Wales: Hemsworth by-election, 1946
- Last by-election in a university constituency: Combined Scottish Universities by-election, 1946
- Last by-election caused by appointment to ministerial office: East Renfrewshire by-election, 1926
- Last by-election from what was to become the Irish Free State: Dublin University by-election, 1919
- Last double member by-election: Stockport by-election, 1920
- Last by-election result to be declared undue: Bristol South East by-election, 1961
- Last by-election result to be declared void: Cirencester by-election, 1892
- First by-election subject to the Corrupt and Illegal Practices Prevention Act 1883: Limerick City by-election, 1883
- First by-election to be held using the secret ballot: Pontefract by-election, 1872
- List of United Kingdom by-elections
- swing (politics)
- Records of members of parliament of the United Kingdom
- UK general election records
- Colin Rallings and Michael Thrasher, British electoral facts, 1832-2006 (Parliamentary Research Services)
- "Labour holds in Cardiff and Manchester but turnout is low". Channel 4 News. Retrieved 16 November 2012.
- South Shields by-election UK Polling Report
- Roy Jenkins Churchill (Macmillan, 2001), page 325 ISBN 0-333-78290-9
- Since the Reform Act 1832; of those whose age can be verified.
- Chris Pond, Parliament and Religious Disabilities Archived September 28, 2007, at the Wayback Machine.
- John M. Clarke (November 1993). "Charles Bradlaugh". Necropolis News. Retrieved 20 April 2017.
- "Manchester Gorton by-election cancellation confirmed". BBC News. BBC. Retrieved 20 April 2017.
- A verdict of accidental death was recorded at the inquest. Clitherow was a Medical Doctor and had taken seven barbitone tablets, described by the pathologist as a "bold dose". See The Times, 19 June 1947, p. 2.
- "Baronetage". Leighrayment.com. Retrieved 2016-10-01.
- [permanent dead link]
- Purdy, Martina. "Mid Ulster by-election: Lutton chosen as unionist candidate - BBC News". Bbc.co.uk. Retrieved 2016-10-01.
- Who's Who of British MPs: Volume IV, 1945-1979 by Michael Stenton and Stephen Lees (Harvester, Brighton, 1979) ISBN 0-85527-335-6
- British Political Facts 1900-1994 by David Butler and Gareth Butler (St. Martin's Press, New York, 1994) ISBN 0-312-12147-4
- Election Statistics 1918-2007. House of Commons Library Research Paper 08/12