A former top foreign ministry official behind the decision to approve Peter Mandelson's appointment as British ambassador to Washington said on Tuesday he had faced "constant pressure" from Prime Minister Keir Starmer's office to speed up the process despite security concerns.

A heated dispute over who should ultimately take the blame for appointing the Labour veteran to Britain's highest diplomatic post despite his past history and known ties to late US sex offender Jeffrey Epstein has piled pressure on Starmer, prompting calls by critics for him to quit.

Starmer has said he was "wrong" to appoint Mandelson to the role and has expressed regret, but on Monday put the blame firmly on officials for failing to tell him that a security vetting body had advised against his appointment - something, he added, that would have stopped him from employing the new ambassador.

Political pressure to appoint Mandelson

On Tuesday, it was time for Olly Robbins, who was sacked late on Thursday after Starmer and foreign minister Yvette Cooper said they had lost confidence in him, to mount his defense.

He was quick to turn the focus on Starmer's office.

"I walked into a situation in which there was already a very, very strong expectation ... that he needed to be in post and in America as quickly as humanly possible," Robbins told the House of Commons Foreign Affairs Committee.

"I think throughout January (2025), honestly, my office, the foreign secretary's office, were under constant pressure," Robbins said.

"There was an atmosphere of constant chasing," he said, describing "very frequent phone calls" from the private office of Starmer's Number 10 Downing Street.

He said the vetting body had advised the appointment was a borderline case and they were leaning against granting clearance - a message Starmer says his government never received.

Robbins said the security concerns about Mandelson did not relate to his relationship with Epstein.

He declined to say when questioned by lawmakers what led the government's vetting agency to flag Mandelson as a potential security risk.

However, Robbins insisted his department "did not bow to that pressure", and said his decision to grant Mandelson clearance was based on security advice that the risks could be managed.

Starmer's judgment questioned

His words are, nevertheless, likely to increase the pressure on Starmer, who after winning the largest majority in modern history for Labour in a general election in 2024 is facing new calls to step down over a scandal which has run for months.

Opposition Conservative Party leader Kemi Badenoch said Robbins’ testimony "is devastating to Keir Starmer."

She said "it is now absolutely clear that 'full due process’ was not followed. Keir Starmer has misled the House" of Commons.

Starmer has denied misleading lawmakers.

Labour MPs have said there would not be an immediate move to oust Starmer over the scandal, especially as the party is expected to suffer big losses in local elections in England and regional votes in Wales and Scotland in just over two weeks.

But the return of the focus on Starmer's Downing Street operation will do little to appease those lawmakers who have repeatedly raised concerns over its operation, criticising what some call a bunker mentality and lack of access.

Mandelson investigation

Mandelson is under police investigation for suspected misconduct in public office after a trove of Epstein-related documents released by the US Department of Justice in January included emails suggesting Mandelson had passed on sensitive, and potentially market-moving, government information to Epstein in 2009, after the global financial crisis.

Starmer fired Mandelson in September, nine months into the job, when new details emerged about his friendship with Epstein.

He has ordered a review into any security concerns arising from Mandelson’s access to sensitive information while ambassador.

British police launched a criminal probe and arrested Mandelson in February.

Mandelson has previously denied wrongdoing and hasn’t been charged.

He does not face allegations of sexual misconduct.