Olly Robbins 'thrown under the bus' in biggest diplomatic crisis in over 40 years, says Lord McDonald

Lord Simon McDonald, the former head of the Foreign Office, has called the Peter Mandelson security vetting scandal "the biggest crisis for the diplomatic service in decades". Speaking on BBC Radio 4's Today programme, Lord McDonald also claimed that Olly Robbins, who was the permanent secretary of the Foreign Office until Thursday when he was asked to step down due to the scandal, was "thrown under a bus" by the prime minister, Keir Starmer and that "No 10 required a scalp and wanted it quickly."

When asked if Robbins had been "basically thrown under the bus", Lord McDonald replied: "Yes. This story broke on Thursday morning in a piece in The Guardian – within the news cycle Olly Robbins had been required to resign. This shows to me that Number 10 wanted a scalp and they wanted it quickly and I cannot see that there was any process, any fairness, any giving him the chance to set out his case, and that feels to me wrong."

McDonald also said that the fallout from Mandelson's appointment had been "the biggest crisis in the diplomatic service" since he joined the Foreign Office in 1982.

The Scottish First Minister John Swinney has become the fifth major party leader to call for Keir Starmer to step down as prime minister. Speaking in Dundee on Saturday, Swinney said that he had "no reason to doubt" that Starmer was telling the truth about his understanding of the process, but still stated that the prime minister's "incompetence" regarding it was "staggering".

Swinney said: "I have no reason to doubt that the prime minister only found out this week, but if he did, it demonstrates a startling level of incompetence that he only found out this week. This issue has been kicking around for months and the prime minister has made very definitive statements to the House of Commons and to other media events where he has definitively said the full vetting process was carried out and left the impression it had been successful. Clearly, he hadn't checked that point and that is a staggering level of incompetence on the appointment of an ambassador to the most significant ambassadorial role."

On the vetting process itself, Lord McDonald said: "These things tend to be a bit murkier than that. I mean security vetting will have incomplete information, they will be unhappy about one or two details, they'll want mitigations to be put in place. And all of that happens quite regularly. It means there are hesitations, there are imperfections, but it doesn't amount to failure. If there had been a failure then that fact – that ultimate conclusion – would have to be conveyed to the political level. But the fact that it was not indicates to me that the picture was more complicated than Number 10 wished to present."

On Friday the Cabinet Office released a template page from the summary document produced by UKSV after Mandelson's vetting. The document lists three rankings for possible "overall concern": low, medium and high. In the next box, there is a space for a vetting officer to list the outcome of the assessment with their "overall decision or recommendation". Again, there are three options: clearance approved, clearance approved "with risk management" or clearance denied.

According to multiple sources, the UKSV process in Mandelson's case concluded there was a "high" overall concern and concluded "clearance denied". It was this recommendation that was overruled by the Foreign Office, which employed a rarely used authority to grant him clearance anyway.

Meanwhile, away from Westminster, Greater Manchester Police says there will be a "significantly increased police presence across the city" as it prepares for a far-right protest organised by Britain First. The march is due to begin from Store Street at 1.15pm and finish at St Peter's Square at around 2pm.

Assistant Chief Constable Rick Jackson said: "Our officers will police without fear or favour, ensuring those exercising their right to protest can do so safely, while intervening when behaviour crossing the line into criminality."

Peter Mandelson's replacement as British ambassador to the US, Sir Christian Turner, said the relationship between the two countries is in the middle of an "extraordinary moment". Speaking in Washington on Friday, he said the transatlantic relationship was still "one of the deepest and closest alliances in history".

He said: "I've now been in this job for about two months, and they said, 'Come to Washington for a rest. It'll be very calm. It'll be very quiet. You'll be okay.' And we're in the middle of this extraordinary moment, geopolitically, geoeconomically, and indeed for the transatlantic relationship."