The vote appears to have been triggered by discontent amongst pro Brexit MPs who are concerned that the present Prime Minister will not obtain a Withdrawal Agreement which will be acceptable to Parliament and might instead, in order to avoid a "no deal" hard Brexit, move to amend the European Union Withdrawal Act 2018 to remove the provision that the UK must leave the European Union on 29 March 2019.

THE PROCEDURE

The procedure was triggered in accordance with the somewhat arcane rules of the Conservative Party.  Once 15% of Conservative MPs (currently 48 out of 330) have requested it, there must be a vote, which should take place "as soon as possible in the circumstances".  In this case it is thought that point was reached during the evening of 11 December.  The vote will take place this evening, between 6 and 8pm.  If Theresa May wins the support of a simple majority of the 315 MPs eligible to vote, she will remain leader of the Conservative Party, and there can be no further leadership challenges for a year.

If she loses, she must resign and a leadership election follows.  However she would resign only as leader of the Conservatives, and would almost certainly remain as Prime Minister.

ELECTING A NEW LEADER OF THE CONSERVATIVES

Any MP who is nominated by two Conservative MPs can stand for election, and in the early stages only Conservative MPs can vote.  It is thought that the hard Brexit element of the Conservatives will choose a single candidate in advance to avoid splitting the vote.  Depending on how many other candidates emerge, there are successive rounds of voting, each eliminating the candidate with the fewest votes, until only two candidates remain.  At that point, unless one of them withdraws, the matter is decided by a postal vote of everyone who has been a member of the Conservative party for three months since the close of nominations.  The last postal ballot, in 2005, took three months.  This would create huge problems for the Brexit process and would almost certainly necessitate a request to the EU to extend the Article 50 process.

It is worth noting, however, that the last leadership election was decided in just over two weeks; of the five original candidates two were eliminated in early rounds and two withdrew.  It may be possible for a new leader to emerge without a postal vote, although given the level of discord amongst Conservative MPs it is difficult to imagine either side withdrawing gracefully.

A NO CONFIDENCE VOTE IN THE GOVERNMENT

A no confidence vote in the Government, as opposed to this no confidence vote in the leader of the Conservatives, may also be proposed by the main Opposition party, Labour.  Under the Fixed-term Parliaments Act 2011, the term of UK Parliaments is set at five calendar years, overriding the previous practice whereby Governments could choose the timing of elections as long as the parliamentary term did not exceed five years.  The Act does provide exceptions; a general election can be called early if Parliament votes by a majority of two thirds, for example, which was the method by which Mrs May called the 2017 election.  The alternative is a no confidence vote in the Government, which can be passed by a simple majority.  The Conservatives do not have a majority at the moment; they signed a "confidence and supply" agreement with the Democratic Unionist Party to secure a majority, but it is not clear whether the DUP would support the Government, given their discontent with the Irish backstop provisions of the current Withdrawal Agreement.  It goes without saying, however, that a general election would also necessitate a request to extend the Brexit process.

>> Read also our Brexit Briefing: What happens now? of 11 December 2018

This Client Alert is not intended to constitute legal advice and should not be taken as a recommendation to take action or withhold from taking action.