Downing Street cannot appoint politicians or business figures to senior diplomatic posts using the same security vetting it uses to check civil servants, a former national security adviser has said.

Peter Ricketts said there had to be more “awkward questions” asked of a person such as Peter Mandelson than the system allows, given “all the baggage” of his three decades in politics and business.

“For that person there must surely be an even more thorough process including detailed interviews with those who have known him/her well in their previous life. That will take time,” Lord Ricketts said.

Other insiders familiar with the appointment process said Mandelson’s appointment was streamlined and the reality was that Downing Street “wanted Peter to be the answer”, with informal concerns brushed off.

One government adviser said they had raised the issue of Mandelson’s association with the Russian billionaire Oleg Deripaska from 2005 – but were told that he was considered “such a master of the dark arts” that it was necessary to appoint him. “Minds had already been made up,” they said.

Mandelson’s appointment on 20 December 2024 was made subject to developed vetting clearance. It was completed in less than two months.

No objections were made by MI5 or MI6, though their involvement in the process run by the Cabinet Office was limited to assessing if there were current issues of national security concern.

Mandelson’s friendship with Jeffrey Epstein had been well reported by the media. The fact the disgraced financier was a known sex offender, while recognised as serious, was not considered a national security matter on a par with terrorism or a hostile state threat.

Nor had Mandelson been vetted before, because ministers are not subject to developed vetting. But it is required for ambassadors and other officials so they can read top secret material, and it is renewed every seven years.

Developed vetting is conducted by a special unit, United Kingdom Security Vetting. An individual must fill in a security questionnaire and submit financial information about themselves and anybody with whom they live or have shared financial liabilities.

There is also a lengthy and intrusive interview in which civil servants are typically asked about their associations, sexual history and habits, use of pornography and drugs as well as their financial affairs. A candidate’s referee is also interviewed The process has been criticised for being insufficiently rigorous.

Arthur Snell, a former UK high commissioner to Trinidad and Tobago, said the process, typically conducted by retired police officers, is not cross-checked beyond the referee, meaning candidates can lie and get away with it.

“You can tell them ‘Oh I never touch drugs, I have very strong views about this’ whilst spending every Saturday night snorting away your salary and, as long as your referee is squared away, the vetters will never know,” he wrote this week.

Information about Mandelson’s Epstein links was collated as part of an initial due diligence report by the Cabinet Office, of which so far only a summary has been published in correspondence with parliament last year.

It included “direct extracts from media reporting and notes a general reputational risk”, and a reference to a meeting between Tony Blair and Epstein facilitated by Mandelson that at that time had not been made public.

Files relating to Epstein released by US authorities last month showed that Mandelson appeared to notify the financier in advance of an €500bn bailout being agreed during the financial crisis in 2010, and that three payments of $25,000 were apparently made to Mandelson between 2003 and 2004. Mandelson said he did not recall receiving those sums.

Mandelson’s appointment was unusual because it was made directly by Downing Street, a rare measure used for a handful of diplomatic postings in the past decade, including that of Ed Llewellyn, David Cameron’s former chief of staff, to the post of UK ambassador to France in 2016.

One person familiar with the process said it had been streamlined, without being considered by a normal civil service appointments panel, which includes outsiders. The prime minister “could have run an interview process, with external people, testing Mandelson and his history properly, but he didn’t do that”, they said.

Last week Keir Starmer said the security vetting processes needed “to be looked at again” because it had not uncovered the “depth and darkness” of ties between Mandelson and Epstein. Other allies such as Steve Reed, the housing secretary, said the spy agencies should have come up with “more information”.

Ricketts said: “There is a real difference between the vetting needed for a professional diplomat who comes to a top job with 30 years of regular vetting and annual staff appraisals – a known quantity – and someone who comes after 30 years in politics or business, with the associated baggage.”