Analyser: May är kvar – men det är även brexitröran

In the United Kingdom, confidence motions are a means of testing the support of the government (executive) in a legislative body, and for the legislature to remove the government from office. A confidence motion may take the form of either a vote of confidence, usually put forward by the government, or a vote of no confidence (or censure motion), usually proposed by the opposition. When such a motion is put to a vote in the legislature, if a vote of confidence is defeated, or a vote of no confidence is passed, then the incumbent government must resign, or call a general election. It is a fundamental principle of the British constitution that the government must retain the confidence of the legislature, as it is not possible for a government to operate effectively without the support of the majority of the people's representatives. At the national level, this means that the UK government (the cabinet) must retain the confidence of a majority in the House of Commons. It is possible for a vote of no confidence to succeed where there is a minority government or a small majority, or where there are internal party splits. Where there is a minority government, the government may seek agreements or pacts with minor parties in order to remain in office. Despite their importance to the British constitution, for a long time the rules surrounding motions of no confidence were dictated solely by convention. However, since the Fixed-term Parliaments Act 2011, a vote of no confidence must be passed in a specific form in order to create the possibility of an early general election. Under the Act, if a motion of no confidence in the government is passed in express terms, the house must then adopt a vote of confidence within 14 days, or a general election is held. A no confidence vote was last successfully used on 28 March 1979, when the minority government of James Callaghan was defeated in a confidence motion which read "That this House has no confidence in Her Majesty's Government". A no confidence vote can have the effect of uniting the ruling party; for this reason such motions are rarely used and successful motions are even rarer. Before 1979 the last successful motion of no confidence occurred in 1924.While motions of no confidence regarding party leadership may have time limits, motions of no-confidence concerning challenges to a ruling government do not and allow for MPs from any political party to participate at any period of time.