The prime minister has refused to be drawn on the leadership ambitions of Andy Burnham but drew a comparison between the Manchester mayor’s economic proposals and the policies of Liz Truss.

Sir Keir Starmer’s comments come after Burnham told the Daily Telegraph he had been been contacted by Labour MPs over the summer urging him to stand.

He also proposed a rival economic vision, including a 50p top rate of income tax and a tax cut for lower earners, in an interview with the New Statesman, further fuelling speculation he is lining up a challenge to the under-pressure leader.

Speaking to the BBC, Sir Keir likened Burnham’s economic suggestions to Truss, who was Tory prime minister for 49 days in 2022, adding she was “a disaster for working people”.

The prime minister said: “I’m not going to get drawn in to commenting on the personal ambitions of the mayor, but I do want to be really clear about our fiscal rules because economic stability is the foundation stone of this government.

“It was three years ago this week that we had the Liz Truss experiment where she abandoned fiscal rules, in her case for tax cuts, and the result was a disaster for working people.

“The same would be true if you abandoned fiscal rules in favour of spending, and I’m not prepared to ever have that inflicted on working people again.”

In the last three weeks the prime minister saw his deputy Angela Rayner forced to quit after underpaying stamp duty and sacked Peter Mandelson as US ambassador after fresh revelations about his relationship with convicted paedophile Jeffrey Epstein.

There is also continuing economic gloom around the cost of living, with November’s budget widely expected to bring in a new wave of taxes to boost the Treasury’s cobwebbed coffers, and worries about Labour’s performance in the local, Welsh and Scottish elections in May.

Burnham has given several interviews ahead of the start of the Labour Party’s autumn conference in Liverpool, where Sir Keir is hoping to pull the spotlight back on to Labour’s successes in government.

Appearing on BBC Radio Manchester this morning, the mayor explained his thinking, saying: “I was asked a direct question by a journalist and I gave an honest answer and that’s been reported today. MPs were in touch with me.”

Burnham was at pains to stress that challenging the prime minister was not a decision for him but for the parliamentary party as he is not an MP.

This need not be a barrier for long, however, should an ally decide to step down to make way for him in a by-election – assuming, of course, that he could get elected standing with a red rosette with Reform UK riding high in the polls.

If he were to win a Westminster seat, this would be Burnham’s third tilt at No 10, having previously lost out to Ed Miliband and Jeremy Corbyn, and he would need the backing of at least 80 MPs.

There does seem to be a supportive cohort of disgruntled Labour MPs, particularly among the 130-strong group who rebelled over welfare reforms and forced Downing Street into a humiliating 11th-hour U-turn.

But a majority of Labour MPs who replied after being contacted by the BBC said they were against seeing Burnham mount a challenge.

BBC Radio 5 Live’s Matt Chorley asked 320 out of the 399 Labour MPs currently sitting in Parliament for comment. Many of the dozens who replied were unhappy at the performance of the Labour government, but few suggested Burnham’s return would improve their fortunes.