Sir Keir Starmer is being accused of sending a "real chill throughout the civil service" by a senior union official, after the PM's decision to sack the lead civil servant in the Foreign Office over the Lord Mandelson vetting fiasco.

Sir Olly Robbins, who gave evidence to the Foreign Affairs Select Committee on Tuesday, was fired as the permanent under secretary at the Foreign Office last week.

Dave Penman, head of the FDA trade union which represents senior civil servants, told BBC Newsnight: "I think the prime minister is losing the ability to work with the civil service.

"Who in the civil service would now think they would be immune from when it is politically expedient to be dismissed?"

"That's not a place any government wants to be because it doesn't deliver for the people of the country," Penman added.

On Monday, Sir Keir sought to play down any sense of a rift with the civil service when he told MPs: "We have thousands of civil servants who act with integrity and professionalism every day."

The row between Downing Street and the union representing senior civil servants is the latest fault line to emerge as a consequence of the most recent revelations relating to the appointment of Lord Mandelson as the UK's ambassador in Washington last year.

Lord Sedwill, who was head of the civil service from 2018 to 2020 and is also a former National Security Adviser, has said the prime minister should "retract his accusations" against Sir Olly and reinstate him.

In a letter to The Times he wrote: "As Robbins explained yesterday, the question for him was not whether to tell the prime minister what he already knew, but whether those issues could be mitigated enough to allow Mandelson access to the secret intelligence necessary to do his job.

"He made the professional judgment that they could. Unwisely as it turned out, he shouldered his responsibilities rather than shunting them."

Supporters of the prime minister have sought to portray the testimony of Sir Olly as vindication that Sir Keir didn't know about the vetting details or, crucially, conclusions Sir Olly had been briefed about.

Work and Pensions Secretary Pat McFadden told BBC Radio 4's Today programme he believed the evidence showed Sir Keir had acted fairly, due to a "fundamental disagreement" between the pair.

He said: "I think the prime minister has acted fairly in these circumstances, because he believes that he should have had that information, that it was relevant to the appointment."

Sir Olly told MPs he was right not to share this in order to protect the integrity of the vetting system.

Pressed on whether he knew if Sir Keir was behind calls to Sir Olly about finding a job for then head of communications at No 10, Matthew Doyle, McFadden said: "No I can't tell you the details of this because I only heard them yesterday though Olly Robbins' evidence."

McFadden added he didn't think Doyle "would have had the qualifications to do that" but "it's not unusual to have conversations when someone is leaving about what they will do".

In a boost to Downing Street's position, Dame Emily Thornberry, the Labour MP who chairs the select committee, said after the hearing on Tuesday that she had also concluded that it was right that Sir Olly had lost his job.

But another Labour MP on that committee, Dan Carden, having heard the same evidence, described No 10's decision to sack Sir Olly as "plain wrong".

In a post on X, he added that "its lasting impact will be to further damage the effective running government that is a responsibility shared between Ministers and civil servants."

But let's take a step back.

This is the seventh day in a row that the self-inflicted damage of the Lord Mandelson saga has rained down on the prime minister, and this element of it over the last week is but a chapter in the wider story.

The minutiae of the prime minister's most politically consequential decision in office are now being forensically dissected and, frequently, in public. At the select committee, in the Commons and in the press.

The building blocks of a judgement call Sir Keir now acknowledges he got catastrophically wrong are being scrutinised daily.

So much for the grid of announcements and campaign events Labour folk in Scotland, Wales and in the areas of England with council elections would love to be focused on. Instead, there is incessant conversation about Lord Mandelson.

And Sir Olly, who was dumped on by Downing Street from a prime ministerial height over the last few days, responded with a modestly expressed assault on its judgement, sense of fairness and proportion.

Granted, they have been gunning for his judgement too, in a circular firing squad about credibility.

With Prime Minister's Questions at lunchtime and the prospect in the coming weeks of the next deluge of documents relating to Lord Mandelson's appointment being published, this is a foul-up Sir Keir is struggling to escape.