Andy Burnham has ruled out standing in a looming by-election and said he was "very likely" to run for a third term as mayor of Greater Manchester.
Rumours had been swirling that the former Cabinet Minister could throw his hat into the ring for an upcoming contest in West Lancashire.
But Mr Burnham said he wouldn't be standing - and complained it was an "annoyance" to be "constantly" asked about his ambitions to be the Labour leader.
West Lancashire MP Rosie Cooper is set to stand down after accepting a job in the NHS, triggering a by-election in her constituency.
Ms Cooper, who was once the target of a neo-Nazi assassination plot, did not confirm when she would quit but Labour is understood to be bracing for a by-election this autumn.
Mr Burnham ruled himself out of the contest in an interview with BBC Radio Manchester and vowed to complete his second mayoral term.
The former frontbencher, who twice ran unsuccessfully to be party leader, was elected as mayor of Greater Manchester in 2017 and re-elected in May 2021.
He said he "firmly believes" that Keir Starmer will be the next Labour PM and described his "frustration" at "constantly" being asked about his leadership ambitions.
"I love what I'm doing," he said. "My heart is in this job. I'm focused on it."
Mr Burnham added: "It kind of has been an annoyance constantly to be asked about that.
"But I've never changed that script. I've always said I'd do a full second term and I will."
He said he was "very, very likely" to stand for a third term, which would rule him out of the 2024 election.
Praising Mr Starmer as "a leader who is speaking for the country, for ordinary people", he added: "I firmly believe he is going to be the next Prime Minister."
However it comes after the Labour veteran set himself at odds with the leadership over tax cuts, electoral reform and universal basic income at the party's annual conference.
He directly contradicted Keir Starmer's assertion that the 1p cut to income tax should go ahead, saying: "I don't think it was a time for tax cuts."
Mr Burnham also backed a campaign to back electoral reform, saying the first past the post system ends up "handing inordinate power over our lives to a tiny elite who often don’t reflect the rest of the country."
In a separate event at The World Transformed festival - running parallel to the Labour conference - Mr Burnham threw his weight behind calls for a universal basic income.
And he also took a swipe at Labour bosses for failing to grant him a slot to give a conference speech.
Mr Burnham said: "I don't make the decisions, and obviously there's pressure on the conference timetable, but I do think where you've got Labour mayors making real positive changes, such as putting a cap on bus fares, which we've done now and people are benefitting from that, let's showcase that."
