SIR Keir Starmer is reflecting on the “political realities” he now faces, a Cabinet minister said today, as pressure mounts over his future as prime minister.

More than 100 Labour MPs — just under a quarter of the parliamentary party — have now called for Sir Keir to go, following Andy Burnham’s victory in the Makerfield by-election on Friday.

Labour grandees including former home secretary Alan Johnson and Lord Falconer have also spoken out, with the latter saying Sir Keir has “no authority.”

Business Secretary Peter Kyle did not rule out reports that Sir Keir could set out a timetable for his departure today, telling Sky News he had “nothing to believe” the reports were true, but added: “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.”

No 10 said Sir Keir’s position remained unchanged from Friday, when he vowed not to “walk away” from Downing Street.

Mr Kyle said “these are decisions for Keir to make.”

Asked if he thought Mr Burnham would make a good prime minister, he said: “I think there is lots of people out there that have the qualifications, the temperament and the qualities to become prime minister.

“Andy Burnham could be one of those people.”

Foreign Secretary Yvette Cooper is among Cabinet ministers reported to have urged Sir Keir to set out a departure timetable.

She declined to comment.

Mr Burnham is due to be sworn in as MP for Makerfield on Monday, with his camp reportedly willing to accept a timetable keeping Sir Keir in post until September.

If he does not resign, 81 MPs would need to back a candidate to trigger a contest.