From 1708 to 1926, members of parliament (MPs) of the House of Commons of Great Britain (and later the United Kingdom) automatically vacated their seats when made ministers in government and had to successfully contest a by-election in order to rejoin the House; such were imported into the constitutions of several colonies of the British Empire, where they were likewise all abolished by the mid-20th century. The requirement of MPs to rejoin the House upon ministerial appointment arose from 17th-century ideas of the independence of the House from the influence of the Crown, which appoints the ministers. Unlike in the United States, whose constitution took such ideas to the extreme by fully separating the executive and legislative branches, support for some royal patronage meant that whilst MPs were barred from keeping their seats when made ministers, ministers holding an existing portfolio were not required to surrender their office when elected as an MP. This resulted in a compromise where newly appointed ministers had to resign from the House, but could keep their office if they won a by-election back into it.
In practice this by-election was usually a formality, uncontested by the opposition, and was gradually reformed starting from the late 19th century; the change of an existing minister's portfolio did not trigger a by-election after 1867, the necessity for by-elections was temporarily suspended during the First World War, and by-elections were no longer needed for ministerial appointments within nine months of a general election after 1919. Ministerial by-elections were criticised as an inconvenience to the government, and were argued to hold back potential executive talent that represented marginal constituencies where a by-election was risky. Nevertheless, supporters of the practice frustrated attempts at its abolition, arguing that it provided a check on the government in an era where general elections were few and far between and allowed a constituency to avoid having its MP appointed to national office without its consent. As parliaments became shorter-lived, the inconvenience of ministerial by-elections to governments became more acute, especially for governments with small majorities and in times where the opposition and special interest groups contested them, and they were abolished in 1926 by a private member's bill.
The Irish Free State, the Union of South Africa, Southern Rhodesia, India, and New Zealand never had ministerial by-elections. In Canada, where such elections had played a role in the King–Byng constitutional crisis of 1926, they were abolished federally in 1931 and in the various provinces between 1926 and 1941; Newfoundland, which would not join Canada until 1949, abolished them in 1928. Australia never had such elections federally, but the states had them prior to the 20th century; Western Australia was the last jurisdiction in the British Empire to maintain such elections, finally abolishing them in 1947.
In many countries with political systems different from the British-derived Westminster system, such as a presidential or dualistic system, executive officers cannot be sitting legislators at the same time. The appointment of a legislator to executive office thus triggers a vacancy in the legislature. If the normal rule for filling these vacancies is holding a by-election, such a country would thus have a form of ministerial by-elections, albeit different from the historical practice in Britain.
Britain
In 1680, the House of Commons of England resolved that accepting an office of profit from the Crown without the House's permission would cause resignation from the House. This was a reaction to the actions of monarchs who attempted to influence the Commons by staffing it with their favourites, or "placemen"; even after the Glorious Revolution of 1688, 120 of the 558 MPs had some sort of patronage from Queen Anne. The Act of Settlement 1701 included a clause barring those holding office under the Crown from membership of the Commons. This, theoretically, produced the system used in the States General of the Netherlands and Parliament of Belgium today, where ministers, though accountable to the assembly, may not sit as legislators. The United States Constitution would later include a similar provision motivated by concerns of executive patronage in the legislature.
However, that clause was not scheduled to come into effect until Anne's death, which would not occur until 1714. In the meantime, Whigs desired to maintain a strong executive for the Hanoverian monarchs who would succeed Anne, whereas Tories wished to check the power of royal placemen. Tory desires to maintain the absolute ban on placemen in the House were narrowly defeated during the making of the Regency Act 1705, while a Whig compromise to limit them to 40 was passed but modified in the House of Lords. The Lords replaced the original list of offices that placemen could hold with a negative list of offices that would disqualify one from the Commons; while the Lords wished mainly to add certain prize offices to those already disqualified from the Commons, Tories in the Commons added several other offices, including all created after 25 October 1705. This process led to a "characteristically illogical English compromise" between those supporting the Crown's ability to dispense patronage and those wishing to bolster the Commons' ability to check the Crown: starting from the Regency Act and continuing with the Succession to the Crown Act 1707, those holding certain offices of profit under the Crown, including ministries, were required to vacate their seats in the Commons, but could maintain their offices if they were re-elected. Commissions in the Army or Navy were expressly exempt from either total disqualification or the requirement for by-election. The requirement to stand in a by-election only applied when an elected legislator was first appointed to a portfolio. Ministers already holding portfolios were not required to contest additional by-elections to remain ministers after being returned in a subsequent general election where their party formed government.
A minister typically sought re-election in the same constituency he had just vacated, but could contest another seat which was also vacant. It was not unusual for an MP representing a safe seat for the governing party to vacate his seat so that a minister might run in it. In the 18th century, it was rare for a new minister to be outright defeated in a by-election; between 1715 and 1754, only eight such occurrences happened between 393 by-elections, and only three defeats occurred from the 460 contests held between 1754 and 1790. The most common cause for a failure of re-election in this era was the ineligibility of the new minister to sit in the Commons, particularly by appointment to the Lords. Also more common than defeat was transferral to a new constituency or retirement. This was largely due to a convention against contesting ministerial by-elections, with breaches being noted in the press. In addition, constituencies of under 500 voters, at the time around 60 per cent of all constituencies, saw roughly 80 per cent of ministerial by-elections. This was because MPs from larger constituencies tended to be gentlemen shying away from government work, and because smaller constituencies were cheaper to manage a campaign.
During the first half of the 19th century, regular by-elections were seen as local affairs whereas ministerial by-elections were seen as a test of the government's record. As the century progressed, however, this distinction was lost and all by-elections were seen as the concern of national party apparatuses. Most constituencies in this era returned two MPs; the fact that by-electionsincluding ministerial by-electionsentailed the election of only one candidate and thus did not allow for voters to cross parties as in a general election was such that they were often called "single elections", and this intensified the partisan implications of by-elections. Even without ministerial vacancies, by-elections were so common in this era that few years had fewer than 20 or 30, and several had as many as 65. Ministerial by-elections were, however, 28.3 per cent of all by-elections in the period between 1833 and 1867, and 20.8 per cent between 1868 and 1914, and were the most common cause of by-elections in the middle of the 19th century, slightly leading resignation and the deaths of incumbents.
By the mid-19th century, the solidification of responsible government made any fear of ministers being more loyal to the monarch than to Parliament purely academic. Despite this, ministerial by-elections were still justified as a way to hold a government accountable to the electorate. Contesting ministerial by-elections became more acceptable during this time, although convention remained to refrain from challenging a by-election that immediately followed a general election, instead waiting for the middle of the term when the government's mandate had worn down. In an era where parliaments could last as long as seven years, this was no trivial matter, and governments suffered 12 defeats in 54 contests between 1832 and 1868. Conservatives tended to have an easier time being re-elected than Whigs or their successors the Liberals. The large majority of ministerial by-elections, 86 per cent, were nevertheless uncontested between 1832 and 1886.
Reform and abolition
Governments began to resent these elections for several reasons. Apart from annoyance and expense of holding the election itself, they distracted ministers in the critical period after they assumed office, and could cause both a political wound and the loss of an able minister should he be defeated. They were also alleged to deter governments from appointing talented executives to the ministry if they represented marginal seats where a by-election could likely be lost, although it is dubious how much this was an issue in practice given the custom of finding safe seats for ministerial candidates. The Reform Act 1867, primarily concerned with expanding the franchise, also included a provision making cabinet reshuffles easier by abolishing the necessity to seek re-election for an existing minister taking a new portfolio. This particular provision was introduced by Benjamin Disraeli, and was agreed to by his rival William Ewart Gladstone and approved without division. The principle of ministerial by-elections was not however under attack, although Disraeli disputed the rationale of holding ministerial appointments publicly accountable.
Lord John Russell proposed eliminating ministerial by-elections as early as 1852. His son Lord Amberley proposed abolishing them in 1867, as did Viscount Bury in 1869. Amberley's and Bury's proposals were received negatively by backbenchers in the Commons, who condemned them as machinations to greatly change the constitution without public debate. With respect to the Amberley bill, James White asserted that such an election allowed a constituency to disallow its MP from serving national office and thereby abandoning it, whilst William Harcourt criticised the Bury bill for allowing ministries to form by personal connections without input from the electorate. Harcourt would reverse course when made the Home Secretary in 1880 and facing the resultant contest in Oxford, bemoaning that he was "to consider the question of a cheap and pure supply of water for the people of London ... But how am I to do so when I am kept here by the cheap distribution of more or less beer in Oxford?" Harcourt ultimately lost the election, but was returned unopposed in another for Derby.