Downing Street considered giving the prime minister's then-director of communications Lord Doyle a diplomat role, the former top civil servant at the Foreign Office has said.
Sir Olly Robbins made the claim while giving evidence to the Commons Foreign Affairs Committee about the appointment of Lord Mandelson as US ambassador.
Sir Olly said he felt "quite uncomfortable" after No 10 discussed potentially finding Lord Doyle a head of mission role with him, and told him not to tell the foreign secretary about this.
Lord Doyle said he had never sought such a position, and was not aware of anyone speaking to the Foreign Office about finding a role for him.
No 10 declined to give details about "personnel discussions" - but pointed out Lord Doyle did not take up a role at the Foreign Office after leaving No 10.
The ex-communications chief was made a Labour peer after leaving Downing Street in March 2025, but was suspended from the parliamentary party this February over his links with a convicted sex offender.
He has previously apologised for his past association with Sean Morton, a former Labour councillor in Moray who admitted indecent child image offences in 2017.
It came after the Sunday Times reported that Lord Doyle campaigned for Morton after he was charged with possessing and distributing indecent images of children in December 2016.
Lord Doyle has said his support for Morton's election campaign came at a time when he was maintaining his innocence.
Sir Olly was sacked last week after it emerged his department had given Lord Mandelson security clearance, despite concerns being raised during the vetting process.
During his appearance in front of the Foreign Affairs Committee, he was asked if No 10 proposed any other political appointees for roles during his time leading the Foreign Office.
In response, he told MPs No 10 was "interested in potential diplomatic options for Doyle" and there were "several discussions initiated by No 10 with me about potentially finding a head of mission opportunity" for him, while he was serving as the PM's director of communications.
"I was under strict instruction not to discuss that with the then foreign secretary, which was uncomfortable," he said.
He added that he was unsure "who exactly was behind" the suggestion or "how serious it was".
Sir Olly said the proposal came shortly after he took over leading the Foreign Office in January last year, at a time when potential job losses were being discussed at his department.
"I found it very hard to think how I would explain to the office what the credentials of Matthew [Doyle] were to be in an important head of mission role when I was in danger of making very senior, very experienced diplomats leave the office," he said.
Sir Olly added that he "felt quite uncomfortable about it" and kept "giving advice that I thought this would be very hard for the office and was hard for me personally to defend".
He claimed Lord Mandelson was also asked about the prospect of a role in Washington for Lord Doyle.
Asked about the claims in the House of Commons, current Foreign Secretary Yvette Cooper, who was not in the post at the time, said she was "extremely concerned" at any suggestion senior civil servants would be told not to inform the foreign secretary.
She added that Lord Doyle "would not have been an appropriate appointment".
In a statement after the committee hearing, Lord Doyle said: "I have never sought any head of mission, ambassador or any equivalent leadership-type posting.
"I was never aware of anyone speaking to the FCDO [Foreign, Commonwealth and Development Office] about such a role for me."
Sir Keir Starmer has faced criticism for his decision to appoint Lord Doyle to the House of Lords.
The row raised further questions about the PM's judgement, after Sir Keir's decision to appoint Lord Mandelson as the UK's ambassador to the US, despite knowing about his friendship with convicted sex offender Jeffrey Epstein.
The latest revelations about Lord Doyle are already going down badly with Labour MPs.
Emily Thornberry, who chairs the Foreign Affairs Committee, said if the claims were true "it shows an arrogance amongst some people at No 10... where they just feel they can do what they want".
"To use the Foreign Office for sort of vanity projects in this way is unforgiveable," she told BBC Radio 4's World at One programme.
One senior Labour figure told the BBC that backbenchers believe that this "through one example shows the character and culture of this government and how it's run".
Labour Party campaign group Mainstream said it showed a "culture of centralisation and patronage" at the top of the party was enabling "catastrophic mis-steps and undermining our relationship with the public".
Liberal Democrat leader Sir Ed Davey said Sir Olly's claims about Lord Doyle were "incredibly damning for Keir Starmer".
He said they showed "not just a lapse in judgement" but "a pattern of behaviour".
SNP Westminster leader Stephen Flynn said Sir Keir had ignored warnings about Lord Doyle's connections with a convicted sex offender.
"And it now turns out he had even higher hopes for Doyle. Just extraordinary," he wrote on social media.
Like Lord Mandelson, Lord Doyle has a long history as an influential figure on the right of the Labour Party.
The veteran Labour spin doctor was the party's head of press between 1998 and 2005, before working for Lord Blunkett and Sir Tony Blair.
He resigned as Sir Keir's head of communications in March 2025 and was given a peerage by the PM last December.
Responding to the Sunday Times report in December about Lord Doyle's previous campaigning for Morton, after his peerage was announced, No 10 told the newspaper the pair's past association was "thoroughly investigated, including through several interviews with Matthew Doyle, prior to his appointment".
However, defending the appointment earlier this year, Sir Keir said Lord Doyle "did not give a full account" of his links to Morton.
Correction 21 April: An earlier version of this article said incorrectly that Lord Doyle was suspended from the House of Lords whereas he was in fact suspended from the Labour Party in the Lords.
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