The number of UK by-elections by session and by Parliament since 1945Jump to full report >>
This list notes the number of by-elections by session since 1945-46 and also gives the results for by-elections since 2005.
A larger version of this chart can be found in the spreadsheet.
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. There have been two by-elections in the current 2017 Parliament.
The by-elections page of the Parliament website provides detailed information on results, including the number of votes cast and percentage share.
See the Commons briefing on UK Election Statistics: 1918-2010 for a list of all by-elections in Great Britain and Northern Ireland.
Please send any comments or corrections to: Parliamentary Information Lists Editor, Parliament and Constitution Centre, House of Commons, SW1A 0AA. Suggestions for new lists welcomed.