Documents to download

Chart showing 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

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.


Please send any comments or corrections to the Parliament & Constitution Centre. Suggestions for new lists welcomed.

Documents to download

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