Five weeks to a new Prime Minister: the rules and timetable that will decide Labour's leader

Sir Keir Starmer's decision to stand down as Labour leader and Prime Minister on 22 June has set in motion one of the fastest leadership contests in the party's modern history. Within hours of his statement, attention turned from the question of whether he would go to the far more consequential matter of how his successor will be chosen, and how quickly.

Because the winner will not merely lead the Labour Party but also walk into Downing Street, the stakes could hardly be higher. The party's rulebook, drafted with internal democracy rather than national crisis in mind, now has to deliver a Prime Minister in a matter of weeks.

The National Executive Committee, which controls the machinery of any contest, met to agree a compressed timetable designed to install a new leader before Parliament returns in September.

The timetable

Sir Keir confirmed in his resignation speech that the contest would formally begin on 9 July, when MPs can start gathering the nominations they need to get on the ballot. The window is deliberately tight, reflecting both the urgency of the moment and a desire among many MPs to avoid a drawn-out summer of internal warfare.

Under the agreed schedule, nominations close on 16 July. If more than one candidate clears the threshold, members will vote over the summer, with the result of any contested election due by 1 September, in good time for the autumn parliamentary session.

• 9 July: nominations open and MPs begin seeking support
• 16 July: nominations close
• By 1 September: result declared in the event of a contest
• September: new leader in place before Parliament returns

The nomination hurdle

To appear on the ballot, a candidate must be nominated by at least 20% of the Parliamentary Labour Party, a figure that currently translates to 81 MPs. It is a high bar, and one that has historically thinned the field dramatically before members get a say.

There is a second gate too. Candidates must also win the backing of either 5% of constituency Labour parties or at least three affiliates, including a minimum of two trade unions, representing 5% of affiliate membership. Taken together, party officials note, the structure effectively limits the contest to a maximum of five candidates.

“Candidates need backing from at least 20% of Parliamentary Labour Party members, meaning 81 MPs would be required.”

— LabourList summary of Labour Party rules

Who votes, and how

If a contest goes ahead, it will be decided by one member, one vote. Every party member with at least six months' continuous membership before the ballot is announced will be entitled to take part, alongside eligible registered and affiliated supporters.

The ballot is preferential: members rank the candidates in order of preference. A candidate must win more than half of all votes cast to be declared the winner. If no one reaches that threshold on first preferences, the lowest-placed candidate is eliminated and their votes redistributed until someone crosses the line.

Background

The contest is administered independently of the candidates. The party's general secretary, Hollie Ridley, acts as returning officer, appointing a legal adviser and an independent scrutineer to oversee the ballot. The NEC retains the power to set and, if necessary, adjust the timetable.

That independence matters because the result will be scrutinised not just by the party but by the country. The eventual winner inherits a governing majority, a turbulent economy and a Reform UK opposition that has consistently led the national polls.

What happens next: nominations open on 9 July, and the first real test will be whether anyone other than the early frontrunner can assemble 81 MPs before the 16 July deadline. If only one candidate clears the bar, Britain could have a new Prime Minister without a single member casting a vote.