A key ally of Keir Starmer hinted that the PM is on the verge of setting a departure timetable today.
Darren Jones said he would not 'get ahead of any decision' when asked whether the PM would lead the party into the next election.
Sir Keir's grip on power appears to be sliding after Cabinet members privately urged him to make a graceful exit in the wake of disastrous local elections.
Around 80 MPs have now publicly called for his resignation, while five ministerial aides have walked out.
One of them, Joe Morris, is an aide to Health Secretary Wes Streeting, seen as the Blairite candidate to replace the PM.
The MP in the seat next to his in east London is also among the rebels, fuelling Left-wing panic that he is behind the coup.
The premier will confront his senior team at the weekly Cabinet this morning, which could be a critical moment.
Darren Jones said he would not 'get ahead of any decision' when asked whether the PM would lead the party into the next election
Ms Rayner acted last night amid worries on the Left that Blairite Wes Streeting is in pole position to take over from Sir Keir if there is an immediate contest
Mr Jones was sent out by Downing Street to brave TV studios this morning.
He told Sky News: 'I spoke to the Prime Minister last night, as you would expect, and he, as you would also expect, is talking to colleagues who have raised issues yesterday.
'But he was also very clear, as I'm sure all of my colleagues are, that coming into the office this morning, as we all are doing, we're absolutely focused on our jobs, on delivering the things that we promise to deliver for the public.'
Asked if Sir Keir would be leading Labour into the next election, Mr Jones said: 'I'm not going to get ahead of any decision that the Prime Minister may or may not take.
'He was very clear yesterday that he will not be walking away, as some of my colleagues have asked him to do...
'All I would say is that the vast majority of us are focused on using the time we have in government to be able to deliver the types of change for people across the country that we're also passionate about delivering, but that we have to work together then as a party in this new political era of five-party politics, of the rise of populist parties in our country, to be able to set the course for winning that next election.'
The decision by five ministerial aides - the others are Tom Rutland, Sally Jameson, Naushabah Khan and Melanie Ward - looked to be part of a coordinated move against the PM.
Ward was previously aide to Deputy Prime Minister David Lammy and tonight called for a 'rapid process for the election' of a new leader.
The timetable for appointing a new Prime Minister is emerging as the critical issue as Blairites and the hard Left wrestle for control of the party.
The latter want a delay so Manchester Mayor Andy Burnham has a chance to win a by-election and return to the Commons - while Streeting would be favourite if the contest is resolved quickly.