Ed Miliband will support Andy Burnham's potential leadership bid against Keir Starmer in return for being made chancellor, allies of the energy secretary have said.
The former Labour leader has ruled himself out as a candidate but wants to act as a 'kingmaker' for Burnham - mayor of Greater Manchester - and usurp Rachel Reeves as chancellor.
Labour faces a likely meltdown in this week's local elections, but Miliband could back Starmer to give time for Burnham to become an MP and face the prime minister down.
Starmer's former deputy Angela Rayner is also known to be considering an assault on party leadership, alongside health secretary Wes Streeting.
But Miliband has 'reservations' on Rayner, a source said, and speculated that Burnham would be a better prime minister.
Centre-Left Burnham was snubbed as a candidate at the Gorton and Denton by-election in February as fears for his potential leadership bid flared. Labour lost the seat to the Green Party.
But on Sunday, the National Executive Committee - which selects candidates for by-elections - said they would no longer block Burnham's return to Parliament should another MP give up their seat.
If Burnham wins leadership, Miliband is expected to be made chancellor, though no formal deal has been signed.
Ed Miliband will back Greater Manchester mayor Andy Burnham in his potential leadership bid in return for being made chancellor if he wins, his allies have said
Andy Burnham is not an MP and was snubbed as a candidate for the Gorton and Denton by-election in February but the National Executive Committee has said it would not block his return to Parliament if the opportunity arose again
'Ed is hugely influential in the party, and people underestimate him at their own peril,' one MP told The Sunday Times.
'He absolutely doesn't want the leadership for himself but does see a role as being a kingmaker for Andy.'
Miliband is close to Lucy Powell, Labour's deputy leader, who also backs Burnham - both had called for him to be allowed to stand in the by-election.
Miliband believes Burnham will win over the 'soft left' vote over Rayner, and allied MPs agree 'momentum has definitely swung away' from her.
Publicly, Miliband backs Starmer. He personally rang backbenchers to dissuade them from voting for the Mandelson inquiry last week.
Some MPs have speculated Starmer could reshuffle his cabinet following the elections and could keep Miliband loyal by offering him Reeves' job.
Downing Street denied an imminent reshuffle.