Keir Starmer has insisted he “won’t walk away” from Downing Street, but it soon won’t be his decision to make.

A Labour leadership contest is coming, after which the prime minister will be forced out of No.10.

If there was any doubt at all, then they will be extinguished next Thursday, when HuffPost UK understand the next tranche of Peter Mandelson documents will be released. They will not reflect well on Starmer.

The only questions that remain are when he will walk out of the famous black door for the final time as PM, and who his replacement will be.

For now, the PM and his allies remain defiant – although the radio silence from Starmer himself in recent days speaks to the turmoil which is engulfing him and the entire Downing Street operation.

Instead, it has been up to loyal Starmer lieutenants like communities secretary Steve Reed to go out and defend the leader. 

“Keir Starmer is the elected leader of the Labour Party and the elected prime minister of our country and as things stand, there is no challenger to him in those positions,” he told the BBC on Friday.

That much is true, of course. Contrary to the expectation at Westminster, Wes Streeting did not trigger a leadership contest when he resigned as health secretary with a furious blast at Starmer.

He even said the debate about Labour’s future “needs to be broad, and it needs the best possible field of candidates” – code for ‘Andy Burnham should be able to take part’.

His critics – and there are many of them in Labour circles – suggested this was because he had failed to get enough support from MPs and so was looking to do a deal with the Greater Manchester mayor.

But this was denied by Streeting allies, one of whom told HuffPost UK: “He has the numbers and will be a candidate when there’s a contest. He doesn’t believe in stitch-ups.”

No contest will take place, however, before we know the outcome of the Makerfield by-election, which was triggered on Thursday when the sitting MP, Josh Simons, resigned to give Burnham an avenue back to Westminster.

Labour’s national executive committee (NEC) will not block his bid to be the candidate, but Burnham still faces an almighty battle to defend the party’s 5,399 majority in the seat from Reform UK.

No date has been set for the by-election, but some time in July has been discussed. If he wins, Burnham already has the backing from enough Labour MPs to challenge Starmer almost immediately.

As party leader, the PM’s name would automatically go on the ballot paper should he want it to, although if he was up against Burnham his chances of victory would be slim to non-existent.

Here, HuffPost UK looks at the runners and riders in the race to replace the PM.

Andy Burnham 

Burnham was an MP until 2017, and during his 16 years in parliament served as a junior minister under Tony Blair and in Gordon Brown’s cabinet. He also tried and failed to be elected Labour leader in 2010 and 2015.

In the nine years since he quit Westminster, he has been the mayor of Greater Manchester, during which time his stock has continued to rise.

He is undoubtedly the most popular Labour politician in the country, which is confirmed by the fact he was re-elected in 2021 and 2024.

However, he cannot challenge the Labour leadership until he is an MP again – and that is a decision for the people of Makerfield.

Bookies’ odds of being next leader: 4/5

Wes Streeting

It is no secret that the Streeting has long coveted Starmer’s job, and he effectively fired the starting gun on the leadership contest when he resigned from the cabinet on Thursday.

He became an MP on the same day as Starmer in 2015 and was quickly identified as a star of the future.

Streeting is comfortably Labour’s best communicator at Westminster, something which has won him an army of admirers in the party.

However, his Blairite credentials have made him something of a hate figure on the left, while Starmer loyalists have accused him of continually working to undermine the PM.

The fact that any contest would ultimately be decided by Labour Party members puts him at a huge disadvantage, however.

Bookies’ odds: 9/1

Angela Rayner

`The former deputy prime minister was forced to resign from the cabinet last year for failing to pay the correct amount of stamp duty when she bought a flat in Brighton.

But she revealed on Thursday that His Majesty’s Revenue and Customs had cleared her of any wrongdoing – leaving her free to mount a leadership bid.

“Whatever role I can play, I will keep pushing and pushing hard because I want the people out there at the moment who are really struggling … to know that I’m putting all my energy into fighting for them,” she said.

She insisted she would not be the one to trigger a leadership contest, but would not rule out joining in if one is triggered.

Bookies’ odds: 5/1

Ed Miliband

The Labour leader between 2010 and 2015, Miliband led the party to a shattering general election defeat to David Cameron’s Tories that year and was forced to resign.

After five years in the political wilderness, during which time he established a cult following online, he returned to the Labour frontbench when Starmer became leader in 2020.

Seen as a Net Zero zealot, he is bitterly opposed to issuing any new licences for oil and gas exploration in the North Sea. Starmer did try to move from the energy brief in a reshuffle last September, but Miliband refused to go and kept his job.

He is one of five cabinet ministers who have privately told Starmer to consider his position, and like Rayner could throw his hat into the ring as the soft-left candidate in any leadership contest.

Bookies’ odds: 7/1

Yvette Cooper

Like Burnham, she also ran for the Labour leadership in 2015, but came in a distant third place as Jeremy Corbyn swept to victory.

Another to have served in the Blair and Brown governments, she is currently foreign secretary and had been seen as a Miliband loyalist.

However, she notably did not give the PM her support in the wake of last week’s disastrous local elections, and Labour insiders say she has been on leadership manoeuvres in recent months. Could be persuaded to challenge Streeting.

Bookies’ odds: 22/1

Shabana Mahmood

The hardline home secretary is firmly on the Labour right, and has angered many in the party with her strict immigration policies.

Known as a straight-talker and good communicator, but her chances of being elected leader by the party’s more left-of-centre membership are slim.

She has also told Starmer that his time in No.10 is up.

Bookies’ odds: 22/1

John Healey

The defence secretary also told Starmer that his time was up, but has since urged his colleagues not to bring him down.

In a post on X on Tuesday, Healey said: “More instability is not in Britain’s interest. Our full focus now must be on dealing with immediate economic & security challenges.”

Another on the soft-left of the party, he is seen as a leadership dark horse, but could be persuaded to run as a unity candidate who could help heal the party after months of bitter infighting.

Bookies’ odds: 33/1 

Other names in the frame

MPs who could also be tempted to challenge for the leadership, if a contest is triggered, include defence minister Al Carns (12/1), Labour deputy leader Lucy Powell (35/1),chief secretary to the prime minister Darren Jones (40/1)and education secretary Bridget Phillipson (35/1).

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