One of Keir Starmer's Cabinet allies has failed to deny claims that Keir Starmer is poised to quit tomorrow amid feverish speculation about the Prime Minister's future.

Peter Kyle, the Business Secretary, did not knock back reports that Sir Keir will announce as early as Monday that he is leaving Downing Street.

The PM is said to have reached the conclusion that his position is no longer tenable after talking to Cabinet colleagues, No 10 advisers, union leaders and key Labour donors.

Sources insisted Sir Keir, who is this weekend discussing his future with his wife Victoria at their country retreat Chequers, had yet to make a final decision. 

Mr Kyle confirmed that Sir Keir was reflecting 'on the political realities and challenges' in the wake of Andy Burnham's thumping win in the Makerfield by-election, which sparked fresh calls from Labour MPs for Sir Keir to quit.

The PM is now under huge pressure to set out a timetable for his departure and to make way for Mr Burnham - the former Greater Manchester mayor.

Asked about the reports the PM is planning to announce his resignation, Mr Kyle told Sky News: 'I have nothing to believe that they are true. I'm seeing a lot of speculation out there. 

'The only thing I can say with fact is that the Prime Minister is hard at work, as he is every day - he is one of the most hard-working people I've ever come across.

'Today, as in every other day I have ever known Keir, he is out there working hard.

'At the same time he is also trying to create the space where he can think and reflect on the political realities and challenges and the opportunities that lie before us.'

Asked if Sir Keir had now come to the conclusion it is in the interests of the country for him to resign, Mr Kyle said: 'All I know for fact is that he is engaging in conversations with a wide range of people, including myself.

'He is, as well as working really hard over this weekend, I think he is making time to reflect on the political realities, challenges and opportunities that he finds himself in.

'I think that is what people would expect him to be doing at this moment in time.'

Downing Street responded to the reports that Sir Keir is poised to quit by insisting the position was unchanged from Friday when the PM vowed to fight on and said that he would not walk away from a leadership challenge.

Sir Keir said then: 'If there is a contest, yes, I will run. I have said repeatedly I am not going to walk away from that.'

A Labour peer claimed the PM would not 'walk away' from Downing Street and create a political vacuum. Instead, he would 'arrange a slow march as a matter of duty and dignity'.

Mr Burnham, who trounced Reform UK at last week's by-election in the Greater Manchester seat, will be sworn in as an MP tomorrow.

Sir Keir is under pressure to make his intentions clear before Tuesday's Cabinet meeting. Another Labour grandee said: 'He's come up hard against the reality that the support isn't there.

'The truth is everyone knows this is no longer a tenable proposition. There's a sadness about it all but sometimes there's just an inevitability in politics.'