Jeremy Corbyn has said that he won’t lead Labour into the next election, after the party suffered its worst defeat since 1935. So who might be thinking about succeeding him? Here are some of the potential runners and riders, with analysis from BBC Reality Check.
Who will run for Labour leadership?
The 57-year old shadow Brexit secretary is currently the bookies’ favourite. He is likely to be seen as the centrist candidate in the race. A passionate Remainer, he was director of public prosecutions before entering Parliament.
The 40-year old shadow business secretary is one of a new generation of MPs on the left of the party who is close to Mr Corbyn’s inner circle. She represented Labour in a TV debate during the election.
The 39-year old was a care worker and Unison official before becoming an MP. The shadow education secretary says she is on the “soft left” of the party.
The 38-year old Birmingham Yardley MP has been one of the most outspoken critics of Jeremy Corbyn’s leadership and the party’s record on tackling anti-Semitism, bullying and harassment.
The 59-year old shadow foreign secretary deputised for Mr Corbyn at prime minister’s questions but was replaced after publicly calling for Labour to back another Brexit referendum.
Other possible candidates include former cabinet minister Yvette Cooper, who lost out to Jeremy Corbyn in 2015, former BBC journalist Clive Lewis and Wigan MP Lisa Nandy. The current shadow chancellor, John McDonnell, has ruled himself out of the contest.
When could it happen?
Jeremy Corbyn has said that it’s up to the National Executive Committee (NEC) – Labour’s governing body – to decide when he goes as leader.
He has said that he expects a new leader to be selected early in the new year.
The party’s rulebook says that when both the leader and deputy leader are “permanently unavailable”, the NEC calls a postal ballot. Deputy leader Tom Watson stood down on 12 December.
The NEC may want to have a new leader in place before local elections in England, scheduled for 7 May.
In 2015, the process took more than four months. Ed Miliband resigned on 8 May and Jeremy Corbyn was announced as winner on 12 September.
Who can run?
The Labour rulebook doesn’t say that only MPs can run, but it is almost certain that the candidates would be MPs.
Candidates for leader and deputy leader need nominations from 10% of Labour MPs and MEPs.
And in a new rule, candidates also need nominations from 5% of Labour’s constituency parties.
Alternatively, they need nominations from three affiliated bodies, two of which must be trades unions, adding up to 5% of affiliated members.
Who can vote?
Members of the Labour Party, affiliated trades unions (if they opt in), and socialist societies such as the Fabians, all get one vote each.
In 2015, non-members were allowed to register as supporters and vote in the contest for a £3 fee.
Those new registered supporters voted overwhelmingly for Jeremy Corbyn, though he gained enough support from members and affiliates to win anyway.
In 2016, when Owen Smith challenged Jeremy Corbyn, the cost of registering was raised to £25 and people were given only two days to sign up.
The cost and the time period for registering this time will be in the hands of the NEC.
How does the vote work?
The votes are cast on a one-member, one-vote basis, by preferential ballot.
That means that voters rank the candidates in order of preference. If any candidate gets more than half the votes, they win.
If not, the candidate with the fewest votes is eliminated, and their second preference votes are redistributed.
If that results in any candidate with more than half the votes, they win. If not, the remaining candidate with the fewest votes is eliminated and their votes redistributed, until the contest produces a winner.
Who controls the process?
Labour’s National Executive Committee has 39 members, representing the trades unions, the shadow cabinet, Labour’s elected representatives at local, national and European level, and constituency parties.
Supporters of Jeremy Corbyn and the grassroots campaign group Momentum are strongly represented on the NEC, and they are likely to use their influence to promote a left-wing candidate in the coming election.
What about the deputy leader?
There is also a vacancy for deputy leader, as the incumbent Tom Watson stood down. It would be up to the NEC to decide when to have an election for a new deputy, although it would be cheaper and simpler to hold the votes at the same time.