In the United Kingdom, a parliamentary by-election occurs following a vacancy arising in the House of Commons. They are often seen as a test of the rival political parties' fortunes between general elections.
Members of the House of Commons are not technically permitted to resign. Thus, members wishing to resign or seek re-election are appointed on their own request to an "office of profit under the Crown", either the Steward of the Chiltern Hundreds or the Steward of the Manor of Northstead. Appointment to such an office automatically vacates the Member's seat. A member who resigns in this manner may stand for re-election without resigning from the office of profit.
Moving the writ for a by-election
An election to the House of Commons is formally begun by the issue of a writ by the Clerk of the Crown in Chancery. In the case of a by-election, the Speaker must first issue a warrant to the Clerk of the Crown to allow the Clerk to issue a writ. The most common reason for the Speaker to issue a warrant is that he has been required to do so by a resolution of the House of Commons itself. This requires an MP to move a motion to command the Speaker to issue his warrant. Such motions are moved at the start of proceedings in the House of Commons.
Usual parliamentary convention, codified by the Speaker's Conference in 1973, is that such a motion is moved by the Chief Whip of the party to which the former MP belonged. However, this convention is not always followed, and such a motion can be moved by an MP of another party. This can arise because the former MP did not belong to a party: the writ for the by-election arising from the death of Independent Republican Frank Maguire was moved by Jim Molyneaux, leader of the Ulster Unionist Party; and after Bobby Sands died on hunger strike the writ for a second by-election was moved by Dafydd Elis-Thomas of Plaid Cymru. When all Unionist MPs from Northern Ireland resigned to force by-elections on the Anglo-Irish Agreement, the writs were moved by senior Conservative backbencher Sir Peter Emery.
Since the date on which the writ is issued also fixes the date of the by-election, it is possible (as was done in the Northern Ireland example) to pass a motion requiring the Speaker to issue his warrant on a set future date. This procedure was followed in 1983 when Conservative MP Michael Roberts died on 10 February. On 19 April, Plaid Cymru MP Dafydd Wigley moved that a writ be issued for a by-election in Cardiff North West, explaining that the by-election was being unnecessarily delayed. The Leader of the House of Commons, John Biffen, successfully moved an amendment to provide that the writ would only be issued on 10 May, three months after his death, in accordance with the recommendations of the Speaker's Conference of 1973. In the event, on 9 May the Queen granted a dissolution of Parliament to take place on 13 May; Biffen therefore moved a motion on 10 May to discharge the previous motion. Unnecessary delay was also the explanation given for the decision of the Liberal Democrats to move the writ for the Oldham East and Saddleworth by-election in December 2010, despite the former MP having been from the Labour Party.
As moving a writ for a by-election takes priority over all other business, MPs sometimes use it as a filibustering tactic. This has been done twice by Dennis Skinner; in 1985 he scuppered a Private Member's Bill banning stem-cell research from Enoch Powell by talking extensively when moving the writ for the Brecon and Radnor by-election, and, in January 1989 he moved the writ for the Richmond (Yorks) by-election and spoke for over three hours so as to prevent Ann Widdecombe from moving a motion to grant extra time to her attempt to restrict abortion laws.
Writs in a recess
When Parliament is not sitting, the Speaker may be required to issue his writ during a recess. The first legal provision for a by-election writ to be moved in the recess was the Recess Elections Act 1784 (24 Geo. 3. Sess. 2. c. 26), which remained in force until replaced by the Recess Elections Act 1975 (1975 c. 66) on 12 December 1975. The procedure for issuing a writ involves two MPs presenting the Speaker with a certificate stating that there is a vacancy. The Speaker must then publish notice of his receiving the certificate in the London Gazette; six days after inserting the notice in the London Gazette, the Speaker will issue a warrant for the new writ. Recess writs cannot be issued where the vacancy has arisen as a result of an MP resigning. The Speaker is empowered to appoint between three and seven senior MPs to exercise his powers to issue recess writs when he is out of the country or there is no Speaker.
Under section 33 of the Bankruptcy Act 1883 (46 & 47 Vict. c. 52), where a Member of Parliament is declared bankrupt, they are granted a period of six months to discharge themselves. At the end of that time the court which ordered the bankruptcy is required to notify the Speaker, and the seat is vacated. The Speaker is required to insert a notice in the London Gazette of the fact and then to issue a warrant for a new writ after six days.
If it comes to light that a vacancy has not properly been declared, a writ for a by-election can be cancelled by a further writ of supersedeas. The last such occasion was in 1880 when Henry Strutt (Member for Berwick-upon-Tweed) succeeded to the Peerage as Baron Belper; a writ was issued on 6 July, before Strutt had received a Writ of Summons to the House of Lords, and so the Liberal Chief Whip moved on 8 July for a writ of supersedeas to be issued.
If the polling day for a by-election is overtaken by a dissolution of Parliament, the writ is automatically cancelled. The most recent cancellation of a planned by-election was in Manchester Gorton which was due to take place on 4 May 2017, on the same day as the local elections, but was cancelled when Prime Minister Theresa May called a snap general election for 8 June 2017 and Parliament was dissolved before 4 May. The previous such occasion was in 1924 when a writ for a by-election in London University was issued during the recess on 22 September 1924. Four candidates were nominated when nominations closed on 1 October, with polling scheduled for 13–17 October. When the government fell over the Campbell Case, the Prime Minister obtained a snap dissolution on 9 October, and the by-election did not take place.
A Speaker's Conference on electoral law in 1973 proposed several changes to how by-elections are usually conducted:
1. The Conference, conscious that the intervals before the issue of by-election writs have on occasion been unduly prolonged, put forward the following guidelines:
(a) The motion for a writ for a by-election should normally be moved within three months of a vacancy arising.
(b) It is inexpedient for by-elections to be held in August, or at the time of local elections in April/May, or in the period from mid-December to mid-February before (under present arrangements) a new Register is issued.
(c) Consequently, if this restriction should bring the date of the by-election into one of these periods, the by-election should if practicable be held earlier. If this is impractical the period should be lengthened by the shortest possible additional time. The total period (from vacancy to the moving of the writ) should not be more than four months.
(d) In the fifth year of a Parliament, some relaxation of these guidelines should be allowed, in order if possible to avoid by-elections being held immediately before a general election.
The Speaker's Conference recommended that these provisions should be embodied in a resolution of the House, but no such resolution has been proposed.
This section needs expansion. You can help by adding to it. (January 2011)
By-elections are often seen as tests of the popularity of the government of the day, and attract considerable media attention. Voters, knowing that the result will rarely overturn a government's majority in the Commons, may vote differently from their normal voting patterns at general elections. By-elections may reflect specific local issues, and often have lower turnout. Thus large changes in vote share can happen, and the results of by-elections can affect or highlight political parties' fortunes, as with the sequence of by-election victories by the Liberal Party in 1972–3, and the SNP's win in the 1967 Hamilton by-election.
In some cases, an MP or MPs may deliberately trigger a by-election to make a political point, as when all the sitting Unionist MPs in Northern Ireland resigned together in 1986 or as occurred in the 2008 Haltemprice and Howden by-election.
Particularly notable by-elections
|North Shropshire||16 December 2021||Conservative incumbent Owen Paterson resigned from parliament after being found by the Parliamentary Commissioner for Standards to have breached paid advocacy rules for making three approaches to the Food Standards Agency and four approaches to the Department for International Development in relation to Randox and seven approaches to the Food Standards Agency relating to Lynn’s Country Foods. In the by-election the governing Conservative Party was defeated by the Liberal Democrats with a 34% swing. This by-election was significant because it was considered a safe seat for Conservatives that they had held for all but two of the last 189 years.|
|Hartlepool||6 May 2021||Labour incumbent Mike Hill resigned from parliament after being informed he would face an employment tribunal later in the year relating to allegations of sexual harassment and victimisation. The by-election was considered significant as the Labour Party had retained the seat in 2019, despite many former so-called red wall seats flipping to the Conservatives. In the by-election, the Conservative Party candidate Jill Mortimer won the seat on a 16% swing, becoming the first Conservative candidate to be elected to represent Hartlepool since 1959, and the first woman to represent the seat.|
|Copeland||23 February 2017||Labour incumbent Jamie Reed vacated his seat to take up a job in the nuclear industry. The Conservative Party gained the seat on a swing of 6%, despite it having been held by Labour since its creation. This was the first by-election gain for a government since 1982. The Conservatives retained the seat at the 2017 general election.|
|Richmond Park||1 December 2016||The incumbent Conservative MP, Zac Goldsmith, resigned his seat, and the Conservative whip, in protest at the government's proposal to build a third runway at Heathrow airport. This was less than six months after the referendum on the UK's membership of the European Union, in which Goldsmith had campaigned for a Leave vote, despite his constituents voting heavily in favour of Remain. In the election, his opponents were able to nullify the Heathrow issue and focus voters' attention on the government's handling of Brexit. Despite both the Conservatives and UKIP choosing not to nominate candidates and instead backing Goldsmith, the Liberal Democrat candidate Sarah Olney won the seat with a 21.7% swing. Goldsmith later won the seat back in the 2017 general election by a narrow margin, a majority of 45, before losing it to Olney once again in the 2019 election by 7,766 votes.|
|Glasgow East||24 July 2008||Labour lost its third safest Scottish seat to the SNP with a swing of 22.5%, at a time when the Labour government's popularity was declining, at the time of the credit crunch and with Britain on the verge of its first recession since the early 1990s.|
|Haltemprice and Howden||10 June 2008||Former Shadow Home Secretary David Davis resigned as an MP to trigger a by-election, in order to spark a wider debate on the issue of civil liberties. He was not opposed by Labour nor by the Liberal Democrats. The number of candidates was the greatest in a Westminster election.|
|Wirral South||27 February 1997||A by-election gain for Labour from the Conservatives which left the Conservative government without a majority, just over two months before the general election in which Labour won by a landslide to end 18 years of Conservative government.|
|Eastbourne||18 October 1990||The incumbent Conservative MP, Ian Gow, was killed by the IRA, and in the by-election the seat was lost to the Liberal Democrats. This by-election came in the final weeks of Margaret Thatcher's eleven years as prime minister, when the Conservative government was trailing Labour in the opinion polls largely due to the recent introduction of poll tax.|
|1986 Northern Ireland by-elections||23 January 1986||Unionist MPs resigned over the Anglo-Irish Agreement. All but one of the incumbent MPs were re-elected.|
|Bermondsey||24 February 1983||The largest by-election swing in British history, when Liberal candidate Simon Hughes won the seat with a 44.2% swing against the Labour candidate Peter Tatchell. The extremely bitter campaign, described as the "dirtiest, most violent and homophobic by-election in modern British history" was marked by homophobia against Tatchell. Liberal campaigners published leaflets saying it was "a straight choice" between Liberal and Labour. The tabloid press also vilified Tatchell for both his left-wing and pro-LGBT views, and he was targeted by far-right groups. Tatchell claims he was assaulted in the street over 100 times while canvassing, including two attempts to run him down by car drivers, and that he received 30 death threats, including a bullet posted through his letterbox at night. His phone number and address were published, allegedly by the National Front. Hughes later apologised to Tatchell, and came out as bisexual himself in 2006.|
|Glasgow Hillhead||25 March 1982||Former Labour Home Secretary, and then leader of the SDP, Roy Jenkins, re-entered parliament, months after narrowly missing out on a seat at Warrington, Cheshire, which Labour narrowly retained. Tam Galbraith, who was the former MP, became the last Conservative MP to represent a Glasgow constituency upon his death.|
|Middlesex||February, March, April 1769||Following his expulsion from Parliament, Radical journalist John Wilkes was repeatedly re-elected in a series of by-elections in Middlesex, with Parliament voiding each result. After his third re-election, Parliament ordered the result overturned and the seat transferred to Wilkes's Tory opponent, Henry Luttrell. The events caused a national controversy, and played an important role in the development of British radicalism.|
For a list of by-election results since 2010, see: List of United Kingdom by-elections (2010–present)
For a list of exceptional results and records in the history of by-elections in the United Kingdom, see: United Kingdom by-election records
- CJ [1980-81] 231; Hansard HC 6ser vol 1 col 539.
- CJ [1980-81] 487-8; Hansard, HC 6ser vol 9 col 966.
- CJ [1985-86] 93-4; Hansard, HC 6ser vol 89 cols 139-40.
- CJ [1982-83] 311-3; Hansard HC 6ser vol 41 cols 164-71.
- CJ [1982-83] 365; Hansard, HC 6ser vol 42 col 737.
- "Oldham East by-election to be held on 13 January", BBC News, 15 December 2010
- White, Michael (22 May 2008). "Stem cells: When the Beast of Bolsover snookered Enoch Powell". The Guardian. ISSN 0261-3077. Retrieved 25 June 2019.
- Martin Fletcher, "Blocking tactic thwarts change to abortion law", The Times, 21 January 1989. See also Hansard, HC 6ser vol 145 cols 591-664.
- CJ  280.
- CJ  286; Hansard, 3ser vol 1918-9. There are seven other cases since 1702 of a supersedeas being issued.
- "London University By-Election", The Times, 2 October 1924, p. 16.
- "An Immediate Election", The Times, 10 October 1924, p. 12.
- House of Commons Library Research Paper 09/44, 13 May 2009, "Election Timetables", 
- Government popularity, by-elections and cycles, by S Stray and M Silver
- 10 Worst By-Elections, by Syed Hamad Ali, New Statesman, 25 July 2008
- "Tories in historic by-election Copeland win". BBC. 24 February 2017.
- "Liberals romp home with a giant swing". The Guardian. 25 February 1983. Retrieved 24 May 2022.
- "Bermondsey by-election 1983: homophobia, hatred, smears and xenophobia". The Independent. 24 February 2013. Retrieved 24 May 2022.
- "Peter Tatchell recalls the dirtiest, most violent and anti-gay by-election in modern British history". PinkNews. 24 February 2015. Retrieved 24 May 2022.
- "Simon Hughes: "I'm bisexual"". PinkNews. 26 January 2006. Retrieved 24 May 2022.