Causes of Byelections since the Reform Act
|Cause||Number of Byelections|
|Resignation (voluntary appointment to an office of profit under the crown of an MP who wished to vacate a seat)||1,064|
|Appointment to Ministerial Office (1)||677|
|Succession to the Peerage||235|
|Elevation to the Peerage||217|
|Elections declared void on Petition||193|
|Members seeking re-election (voluntary appointment to an office of profit under the crown of an MP who wished to vacate a seat in order to seek a vote of confidence from their constituents)||51|
|Acceptance of office which necessitated re-election||36|
|Members elected for more than one seat declining those they did not wish to represent||26|
|Disqualification from membership of the House of Commons (2)||16|
|Expulsion from the House of Commons||8|
|Members declared bankrupt (3)||3|
|Creation of a new seat during a Parliament||2|
|Seat vacant for Members having voted before taking the oath (4)||2|
|Member certified as insane (5)||1|
This analysis does not include vacancies for which no byelections were held because of a dissolution of parliament. Much of the research work on which this table is based was undertaken by the late F.W.S. Craig.
Most causes of byelections are matters of common law. The notes list those which derive from statute law.
NB: The 'Reform Act' is the popular title for the Representation of the People Act 1832 (2 & 3 Wm IV, c. 45), the Representation of the People (Scotland) Act 1832 (2 & 3 Wm IV, c. 65), and the Representation of the People (Ireland) Act 1832 (2 & 3 Wm IV, c. 88), with two other related Acts defining constituency boundaries.
- Under the Succession to the Crown Act 1707. The Re-Election of Ministers Act 1919 severely restricted the necessity to seek re-election on appointment to government office. The Re-Election of Ministers Act (1919) Amendment Act 1926 ended the practice.
- A list of offices which are considered Offices of Profit under the Crown and thereby disqualify for membership of the House of Commons is contained in Schedule 1 to the House of Commons Disqualification Act 1975, as amended. The Act gives the Secretary of State the power to amend Schedule 1 by Order in Council on resolution of the House of Commons and is in practice continuously changing. This category also includes other disqualifications:
- Persons who are not British subjects or citizens of the Republic of Ireland (Act of Settlement 1700, as amended).
- Persons under the age of 21 (Parliamentary Elections Act 1695).
- Persons ordained as a priest or deacon of the Church of England, a Minister of the Church of Scotland, and those ordained in the Church of Ireland (House of Commons (Clergy Disqualification) Act 1801). A disqualification applied to the Church of Wales, but was removed when it was disestablished (Welsh Church Act 1914). A person in holy orders in the Roman Catholic Church was also disqualified (Roman Catholic Relief Act 1829). This category of disqualification was severely restricted by the House of Commons (Clergy Disqualification) Act 2001 and now only applies to Lords Spiritual.
- Persons convicted of treason (Forfeiture Act 1870).
- Persons convicted of any offence in any jurisdiction and at the time of the election, in respect of that offence, serving a sentence of more than one years' imprisonment, or unlawfully at large when they should be serving such a sentence (Representation of the People Act 1981).
- Persons reported personally guilty or guilty by their agents of any corrupt practice at an election, such disqualification lasting for 10 years if personally guilty, 7 years if guilty by their agents, for the constituency in respect of which the offence was committed. Persons convicted of a corrupt practice are in addition disqualified for 5 years from representing any constituency. The court has the power to mitigate and remit these incapacities (Representation of the People Act 1983, though the relevant sections re-enacted provisions which were originally contained in the Corrupt and Illegal Practices Prevention Act 1883).
- Persons reported personally guilty or guilty by their agents of any illegal practice at an election, such disqualification lasting for 7 years if personally guilty, for the duration of the Parliament if guilty by their agents, for the constituency in respect of which the offence was committed. The court has the power to mitigate and remit these incapacities (Representation of the People Act 1983, though the relevant sections re-enacted provisions which were originally contained in the Corrupt and Illegal Practices Prevention Act 1883).
- Returning Officers are incapable of being elected for the constituency for which they are responsible for making the return to Parliament, though this does not apply in England and Wales where the whole of a Returning Officers duties are carried out by an acting returning officer.
- It has been held that persons who are deaf and dumb are disqualified (see Whitelocke (1766) vol 1 page 461), but it seems unlikely that this would be upheld in the modern age.
- Under the Bankruptcy Act 1883. This category includes two cases of Irish constituencies where the Bankruptcy Act 1883 did not apply and the situation was governed by the Bankruptcy (Ireland) Amendment Act 1872. Therefore in Ireland, bankruptcy vacated the seat but did not disqualify, and one of the Members successfully sought re-election.
- Of which, 1 deliberately and 1 inadvertently.
- Under the Luncacy (Vacating of Seats) Act 1886. There was at least one case before the passage of this Act of a Member found to be of unsound mind, who could not be deprived of his seat - John Bell, MP for Thirsk in July 1849. The Lunacy (Vacating of Seats) Act 1886 was repealed and replaced by the Mental Health Act 1959 (without the previous provision to fine those disqualified who continue to sit and vote in the House); the Mental Health Act 1959 was itself repealed and replaced by the Mental Health Act 1983.