There’s a growing belief among ministers that Keir Starmer’s latest misstep could be his undoing. “I think he’ll have to resign next week,” one minister confided this morning. The assertion stems from a perceived blunder during Prime Minister’s Questions, where Starmer allegedly misled the House. According to the minister, “Everyone will realize next week that he lied to the House, and that will be the end of it.”

The controversy centers around a statement Starmer made to Conservative leader Kemi Badenoch during a parliamentary debate. He presented quotes from Sir Olly Robbins, the former Foreign Office permanent secretary, suggesting that Robbins had exonerated No10 and the Cabinet Office from undue influence regarding Peter Mandelson’s vetting. However, these quotes were selective, misleading, and in one case, falsely attributed. Starmer went on to boldly claim, “No pressure existed whatsoever in relation to this case.”

This claim has reportedly caused significant concern within No10. Initially described as “deep unease” by a minister, this concern has escalated to outright “panic” by the following morning. The issue seems to stem from the Prime Minister’s deviation from a scripted response prepared by his team. This script was intended to address Sir Olly’s allegations of consistent pressure from January, involving both his office and the Foreign Secretary’s office.

In preparation for Sir Olly’s testimony before the foreign affairs committee, Starmer’s team devised a strategy to counteract the narrative that officials were coerced into expediting Mandelson’s appointment. Acknowledging the reality of the pressure, they opted for a different tactic. The plan was for the Prime Minister to argue that officials should have been resilient enough to withstand any coercion.

This was the approach Starmer initially introduced in his statement to the Commons on Monday, marking the beginning of the current political firestorm.

Keir Starmer has put his team in a state of panic after deviating from his lines during PMQs

He may have misled the Commons by claiming no pressure was put on the Foreign Office

This was precisely the line Sir Keir road-tested in his initial statement to the Commons on Monday.

That day, Lib Dem MP Claire Young put this to the Prime Minister: ‘Ditching a tried and tested ambassador for a high-risk one seems odd behaviour for a Prime Minister who claims to be so fond of proper process. Whose idea was it, and who was applying the pressure?’

Sir Keir responded: ‘I reject the idea that any pressure is a good reason not to disclose to the Prime Minister that UKSV [UK security vetting] recommended against clearance for a very senior, sensitive appointment. I simply do not accept that that is an adequate reason, whatever the pressure.’

But then on Wednesday, for reasons even his closest advisers cannot fathom, he opted to abandon that script – and extemporise. With potentially catastrophic consequences.

Much of Westminster’s focus has been on the news that Sir Keir’s former chief of staff, Morgan McSweeney, is to appear next week before Dame Emily Thornberry’s select committee. But within Downing Street the focus – and fear – is centred on an expected appearance by Sir Philip Barton, Sir Olly’s predecessor.

It is common knowledge within No10, the Cabinet Office and the Foreign Office that Sir Philip was placed under enormous pressure to fast-track Mandelson’s appointment. According to one report, he was ordered by McSweeney to ‘just f*****g make the appointment’.

It’s not clear whether Sir Philip will confirm that specific quote, and McSweeney’s allies insist he would not use such industrial language towards a senior civil servant.

But Downing Street officials do expect Sir Philip to confirm severe pressure was applied. At which point the Prime Minister will be seen to have directly misled Parliament.

‘Barton will deliver the coup-de-grace’, a minister told me. ‘When he directly contradicts what Keir said in the House, there’s no way out.’

The view that Sir Keir’s exit will come as early as next week is not widely shared. The consensus amongst MPs and officials I’ve spoken to is that when Sir Philip’s damning evidence is set alongside the staggering PMQs blunder, it will prove the catalyst for the establishment of a formal inquiry by Parliament’s standards committee. And that could, in turn, be the trigger for Sir Keir’s resignation.

As one minister explained: ‘It was the standards committee that brought Boris down in disgrace. And Keir won’t want that. The optics and parallels will be too damaging. He isn’t going to allow it. He’ll just walk.’

I was talking to another MP yesterday who had watched Sir Keir’s disastrous PMQs performance with mounting horror. I asked them what they thought had provoked the Prime Minister into making such a bizarre blunder. Especially given it came in the middle of a monologue which involved him castigating Badenoch for accusing him of misleading the House and country.

‘I think, subconsciously, there’s part of him that wants it to be over now,’ they said. ‘I think he wants the decision to be taken out of his hands.’

Next week, the Prime Minister may well get his wish.