List of United Kingdom by-elections (2010-present)

This is a list of parliamentary by-elections in the United Kingdom since 2010, with the names of the incumbent and victor and their respective parties. Where seats changed political party at the election, the result is highlighted: blue for a Conservative gain, red for a Labour gain, orange for a Liberal Democrat gain, purple for a UK Independence Party (UKIP) gain and grey for any other gain.

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. Accepting an office of profit under the Crown vacates the member's seat. This process is used because members of the House of Commons are not technically permitted to resign. A member who vacates their seat in this manner may stand for re-election.

There has been one by-election in the current Parliament. This was in a seat held by Sinn Féin and the by-election was won by the incumbent party. It was called as a result of the resignation of the previous MP.

There were 10 by-elections in the 2015–2017 Parliament (with a planned by-election in Manchester Gorton cancelled when the 2017 general election was called). Seven were in seats held by Labour, and three by the governing Conservatives. Eight by-elections were won by the incumbent party, the Conservatives won a seat from Labour and lost one to the Liberal Democrats. Three by-elections were a result of the death of the incumbent MPs, all of whom represented Labour.

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