Does Burnham win mean Starmer's days as PM are numbered?

Andy Burnham's return to Westminster sets up a battle for the UK Prime Minister position, which could see Keir Starmer ousted after Mr Starmer insisted he would fight any leadership challenge.

Mr Burnham defeated Reform UK's Robert Kenyon in the Makerfield by-election by 9,231 votes, up from 5,399 in 2024, and Labour’s vote share increased by 9.61%.

Will a Labour leadership contest be triggered?

This would depend on the new MP for Makerfield, Mr Burnham, or another leadership hopeful, such as former health secretary Wes Streeting, securing the backing of the 81 Labour MPs - 20% of the party’s strength in the Commons (the UK Parliament) - required to mount a challenge.

Mr Burnham’s decision to return to Westminster and give up the Greater Manchester mayor position suggests he is confident he has the numbers required, so the question becomes one of timing - and whether he would be prepared to trigger the contest himself.

Who else could stand in any contest?

As the current leader, Mr Starmer would automatically be on the ballot in any contest – and his defiance of calls to voluntarily stand down this morning makes clear he intends to fight on.

Mr Streeting quit as health secretary in protest at Mr Starmer’s leadership and has indicated he is prepared to be the one to fire the starting gun on a contest by going public with a list of 81 names.

Former Royal Marines officer Al Carns, who quit as armed forces minister in a row over defence funding and the treatment of Northern Ireland veterans, has also hinted he would seek to enter a leadership race.

However, it is unclear whether the MP - who was only elected in 2024 - has the supporters required to get on the ballot paper.

How would a Labour leadership contest work?

After a leadership hopeful nails down 81 backers in the UK Parliament, candidates are then put to a vote among party members, who rank them in order of preference.

A contender is declared the winner if they get more than 50% of first preferences, and this usually happens through a process of elimination during rounds of voting, the timetable for which is set by Labour’s ruling National Executive Committee.

Will the Prime Minister take on his rivals?

He has made clear he certainly intends to, despite both Mr Streeting and Mr Burnham hoping he will use the weekend to accept that a challenge is inevitable and his time in No 10 is over.

The Prime Minister told reporters he would stand if his position is challenged, insisting he will not "walk away" from Downing Street and is focused on "what I was elected to do, which is to serve my country".

What about the Greater Manchester mayor’s position?

Mr Burnham automatically gives up his position as Greater Manchester mayor by becoming Makerfield’s MP, leaving a vacancy in the role he has filled since 2017.

The cost to the taxpayer of holding a vote to replace him - which will run into the millions - was cited by Labour’s ruling NEC as a reason for blocking Mr Burnham from standing in the previous Gorton and Denton by-election.

A mayoral by-election must be held within 35 days of the post becoming free, and the returning officer for the Greater Manchester Combined Authority confirmed that a poll will be held on Thursday 30 July.

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