UK parliamentary by-elections since 1945

Note: This chart is a available in the spreadsheet.

When do by-elections happen?

A by-election occurs when a seat in the House of Commons becomes vacant during the lifetime of a Parliament (ie between general elections), because the sitting MP dies, resigns, is elevated to the peerage, or becomes ineligible to sit for some other reason. 

Further information

The by-elections page of the Parliament website provides detailed information on results, including the number of votes cast and percentage share of the vote.

See the Commons briefing, UK Election Statistics: 1918-2021: A century of elections for a list of all by-elections in Great Britain and Northern Ireland.

Parliament: facts and figures

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This series of publications contains data on various subjects relating to Parliament and Government. Topics include legislation, MPs, select committees, debates, divisions and Parliamentary procedure.

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