Tensions are brewing with the Makerfield by-election tomorrow
Ed Miliband is said to be shunning Sir Keir Starmer as the Energy Secretary prepares to defy his boss and back Andy Burnham as Prime Minister.
The former Labour leader has already been tipped to be in the running to replace Rachel Reeves as Chancellor if the "King of the North" is successful in his bid to win the Makerfield by-election and boot out Sir Keir from No10.
Over the past week, Mr Miliband and Sir Keir are understood to have clashed over making cuts to the former leader's department to funnel more funds into defending Britain.
But he has been accused of declining calls from his boss while the pair remain at a crossroads over the spiralling issue, The Times revealed.
A source close to Mr Miliband denied the claim altogether and insisted the pair did speak in the end.
Mr Miliband eventually accepted a one per cent cut to his Net Zero funding.
However, he remains on Downing Street's "resignation watch", leaving Labour officials "blindsided" when John Healey resigned from the Ministry of Defence last Thursday.
The Energy Secretary and the Manchester mayor have been colleagues for over a decade, even before Mr Miliband became Labour's leader and continue to speak on a regular basis, party insiders said.
The Doncaster North MP has already chipped in with some economic guidance, suggesting obeying Whitehall's fiscal rules to cool the nerves of the bond markets.
"Ed is clearly working on the basis of that is what he wants (to be Chancellor) and that’s what he is assuming he will get," a close ally of Mr Burnham said.
Facing the prospect of packing her bags and leaving No11, allies of Rachel Reeves have been rallying behind the Chancellor, insisting she must not be replaced if the Prime Minister is forced out.
They warned switching out the Leeds West and Pudsey MP could risk "spooking" the markets.
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With the Makerfield by-election just a day away, political tensions are brewing behind the door to No10 as Sir Keir attempts to put a stop to a mounting coup if Mr Burnham is victorious in the contest.
Still, the leadership hopeful is gearing up to issue Sir Keir Starmer a final ultimatum if he is denied a "bloodless coronation" following the Makerfield by-election.
The Mayor of Greater Manchester has already admitted he would seek to replace the Prime Minister upon his return to Westminster.
But he is now said to be planning to tell his boss that he must set out a timetable for his departure or face the wrath of a sudden revolt within his party.
However, Mr Burnham will not tell Sir Keir to resign on the spot, sources say.
Wes Streeting, former Health Secretary, has already told the embattled Prime Minister to establish a timetable for his departure from the top job, adding that it was time to conclude the "drift and uncertainty" of Labour's leadership.
"When the results (from Makerfield) are in, I hope the Prime Minister will, at that stage, reflect on his own position and set out a timetable," the leadership hopeful told reporters yesterday.