Andy Burnham has hit out at allies of Sir Keir Starmer for “demanding simplistic statements of loyalty”, claiming they are underestimating the “peril” Labour is in.

The mayor of Greater Manchester insisted his recent interventions have not been about “personal ambition”, but starting an “open debate” about the direction of the party ahead of potentially catastrophic local and devolved elections next year.

In the lead up to Labour’s annual conference in Liverpool this week, the so-called “King of the North” has accused Sir Keir of having no vision for the country, while setting out his own policy proposals.

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It has fuelled mounting speculation he could launch a future leadership challenge against the prime minister, who in turn has compared Mr Burnham to Liz Truss.

At a fringe event on the opening day of the conference, the Northern mayor said: “I was clear in the interviews I gave last week, I wanted to launch a debate about the direction of the party and getting a plan to beat Reform UK.

“Those out there making calls for simplistic statements of loyalty are underestimating the peril the party is in.”

Two polls this week have predicted Reform UK leader Nigel Farage will become the next prime minister, while a poll of Labour members found more than half of them don’t want Sir Keir to fight the next general election.

Mr Burnham later turned up to a rally about Proportional Representation (PR), in which he insisted he wanted “this government to work”.

He received a rapturous reception as he entered the room, flanked by over a dozen photographers.

Mr Burnham made light of the attention, quipping that “there’s nothing more unstoppable than an idea whose time has come”, in reference to PR.

But this was not the focus of the punchy speech that followed, in which he criticised the Labour leadership’s handling of dissent, saying a “climate of fear” was preventing MPs from having an “open debate” about the direction of the party.

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A handful of Labour MPs have been suspended over the past year for criticising the government on issues like welfare reform and the two child benefit cap, but Mr Burnham has the freedom to be outspoken as he is not a member of parliament.

He said he had been accused of “all sorts of things” in the past week but had done “nothing more than launch a debate”.

Mr Burnham drew clear dividing lines in a recent interview with The New Statesman, as he said the country should be “less in hock to the bond markets”, called for a greater focus on council housing and said public utilities should be nationalised.

It fuelled speculation of an impending leadership challenge, given Mr Burnham fought twice to run the Labour Party while he was an MP, before stepping down in 2017 to run for the metro mayor position. He has not ruled out a return to Westminster and last week claimed Labour MPs have privately asked him to stand.

Sir Keir tried to shut down the narrative by suggesting Mr Burnham’s policies would unleash the economic chaos of Ms Truss, whose fatal mini budget sent the markets into meltdown, as he dismissed the “personal ambitions of the mayor”.

However, in a direct message to “those who say that I’m speaking out purely for my own ambition”, a defiant Mr Burnham said: “I can say to you tonight I am speaking out for the thousands of councillors here at this conference who are worried about going to those doorsteps next May, speaking for the members of the Senedd who, again, are working hard to keep Wales Labour… and, of course, members of the Scottish parliament as well, who want a stronger story about Labour to go to those doorsteps.

“I’m speaking out for the millions of good people around Britain who want a more hopeful direction for the country.

“I think we can do it. I honestly believe it can be done. We can make this government work, we can find that more hopeful direction and we can win again at the next general election.”

The speech was met with a big round of applause from members, while one Labour MP told Sky News it was a “great speech”.

And while cabinet ministers have called for the party to unite behind the prime minister to fight Reform UK – there appeared to a change in tone from Wes Streeting as the first day of conference drew to a close.

The health secretary told a fringe event that the government must be “open to challenge” from within.

He said: “We’ve got to be self-confident enough as ministers to be open to challenge, and openly debate different ideas, because it makes you stronger as a government.”