Former home secretary Alan Johnson has ruled himself out as a contender for the Labour leadership, announcing he will back David Miliband in the upcoming contest to succeed Gordon Brown.
Mr Johnson had long been tipped as a possible successor to Mr Brown and was one of the leading Cabinet cheerleaders for a coalition with the Liberal Democrats which could have resulted in him taking the top job.
But this morning he said that Mr Miliband, the former foreign secretary, was the party's "greatest talent" and should be Labour's new leader.
Asked if he was standing in the leadership contest, Mr Johnson told BBC Radio 4's Today programme: "No, I'm not. I am going to support David Miliband."
His announcement came ahead of a gathering of Labour MPs to consider the way forward in the wake of election defeat.
Harriet Harman has been appointed acting leader until a successor to Mr Brown is chosen.
Labour's ruling National Executive Committee has agreed to to meet "in the days and weeks ahead" to determine the timetable and the procedures for electing a new leader.
As well as Mr Miliband, former cabinet ministers Ed Balls, Andy Burnham and Mr Miliband's brother Ed have been tipped as possible contenders for the party's top job, as well as Labour "greybeard" Jack Straw and influential backbencher Jon Cruddas.
Ms Harman herself has signalled she does not intend to stand if she can retain her previous position of deputy leader.
Would-be leaders of the opposition are expected to start declaring their candidacies over the coming days, and there were signs on Tuesday that hopefuls were beginning to set out their stalls.