List of United Kingdom by-elections (1918–31)
This is a list of parliamentary by-elections in the United Kingdom held between 1918 and 1931, with the names of the incumbent and victor and their respective parties. Where seats changed political party at the election, the result is highlighted: red for a Labour gain, blue for a Conservative gain, orange for a Liberal gain, and grey for any other gain.
- See Resignation from the British House of Commons for more details.
Where the cause of by-election is given as "resignation" or "seeks re-election", this indicates that the incumbent was appointed on his or her 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. These appointments are made as a constitutional device for leaving the House of Commons, whose Members are not permitted to resign.
- Gain retained at the 1922 general election.
- Horatio Bottomley was expelled from the Commons following his imprisonment for fraud. The by-election was won by Clifford Erskine-Bolst as a Conservative candidate supporting the Coalition, who retained the seat in the 1922 general election for the party post Coalition.
- An uncontested by-election.
- Gain not retained at the 1922 general election.
- The seat was regained at the 1922 general election by the National Liberals, as the Coalition Liberals were restyled following the end of the Coalition.
- Thomas Wintringham died later in the Parliament and Louth was retained for the Liberals by his wife Margaret in both the second by-election and the 1922 general election.
- Erskine was the nominee of the Anti-Waste League. In the 1922 general election he was also supported by the St. George's, Hannover Square, Independent Conservative Association who were in dispute with the official Conservative Association in the constituency. During the 1922-1923 Parliament Erskine came to sit as an official Conservative and retained the seat as such in subsequent elections.
- At the time of his election Polson was supported by Horatio Bottomley who formed the Independent Parliamentary Group in Parliament. Shortly after election he joined the newly formed Anti-Waste League. He unsuccessfully defended his seat in the 1922 general election as an Independent Conservative, losing to an official Conservative candidate.
- The Wrekin experienced two by-elections in 1920. Both Charles Frederick Palmer and Sir C. V. F. Townshend were supported by Horatio Bottomley and once in Parliament joined his Independent Parliamentary Group. The seat was won by the Coalition Liberals in the 1918 general election and by the Conservatives in the 1922 general election.
- George Edwards gained South Norfolk from the Liberals, but lost to the Conservatives in the 1922 general election.
- John Edmund Mills won Dartford from the Coalition Liberals, but lost to George William Symonds Jarrett, running as a Constitutionalist in the 1922 general election.
- Spen Valley was taken from the Coalition Liberals by Labour due to the intervention of an anti-Coalition official Liberal. In the 1922 general election the anti-Coalition Liberal gained the seat.
- Due to the establishment of the Parliament of Northern Ireland, the number of constituencies for Northern Ireland was substantially reduced from the 1922 general election. East Antrim was absorbed into the larger two-member Antrim constituency, which at the 1922 election was won by two official Ulster Unionists.