List of United Kingdom by-elections (1979–present)

This is a list of parliamentary by-elections in the United Kingdom held between the 1979 and 2010 general elections, 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, yellow for an SNP gain, orange for a Liberal, SDP or Liberal Democrat 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 resigns in this manner may stand for re-election.

There were 14 by-elections in the 2005–2010 Parliament. Eight were in seats held by the governing Labour party, three by the Conservatives, one by the Liberal Democrats, one by an independent and one by the speaker. Eight by-elections were won by the incumbent party, including in Haltemprice and Howden where Conservative David Davis resigned to recontest his seat. Meanwhile, Blaenau Gwent was won by a second independent candidate. Labour lost four seats; two to the Conservatives, one to the Liberal Democrats and one to the SNP. The speaker's seat was regained by Labour, the party speaker Michael Martin represented before he took up the position. Eight by-elections were a result of the death of the incumbent MP - five Labour MPs died, along with one Liberal Democrat, one Conservative and independent MP Peter Law.

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