Andy Burnham has said he would consider "one day" running for Prime Minister as Labour leader.
The Greater Manchester Mayor insisted he was focusing on his current role - and that he backs Keir Starmer - but suggested he had his eye on the top job.
The former Cabinet Minister has made two unsuccessful bids to lead the Labour Party, losing out to Ed Miliband in 2010 and Jeremy Corbyn in 2015.
He stood down as an MP ahead of the 2017 election and was elected as mayor of Greater Manchester that year.
Mr Burnham, who was dubbed 'King of the North' for his Covid battles with the Government, has been at odds with the leadership at times and piled pressure on Keir Starmer after a row over whether frontbenchers should join picket lines.
Asked if he would consider running to be PM, Mr Burnham told Sky News: "Perhaps one day, if that would be something people would support, but not now because we've got a leader of the Labour Party who is providing leadership during the cost-of-living crisis and I'm happy to give my full support to Keir.
"And I've got a job to do in Greater Manchester ... and I'm making big changes to public transport, which hopefully will get people through this, and that's where my full focus is right now."
He added: "I'm just being honest, in the future, I've said I'll serve a full second term as (mayor).
"If at some point beyond, way beyond this point where we are, that that was something that was a possibility, I would consider it."
Mr Burnham said he would join RMT chief Mick Lynch on a picket line and argued there was nothing "controversial" about workers fighting for better pay.
Asked if he would share a picket line with the union leader, he said: "I would, you know. I don't see this as controversial.
"People are fighting for their incomes in a cost-of-living crisis. Of course you've got to recognise the point that they are making."
It comes after a row in Labour ranks over whether frontbenchers should join picket lines.
Shadow Transport Minister Sam Tarry was sacked last month after giving a string of interviews from a picket line without permission from party HQ, where he backed rail strikes and suggested that workers should get above inflation pay rises.
Labour's approach is to criticise the Government for failing to resolve the issue, rather than publicly backing industrial action.
It is also not calling for inflation-busting pay hikes.
Mr Starmer said he had been fired for "making up policy on the hoof" but the move sparked anger from some union bosses and left-wing MPs.
