Top figures involved in the honours process have claimed they faced pressure from No10 to hand gongs to favoured candidates, including a Tory donor.
Former members of the Honours Committees told Channel 4 that they felt that Downing Street was trying to influence their decisions - and when they pushed back, they were told their services were no longer required.
Dame Louise Casey, who currently chairs the Community and Voluntary Service Committee which awards the majority of honours, wrote a damning email to the Cabinet Office earlier this month warning about the “politicalisation” of the system.
Labour warned that "underhand attempts to game the system to reward a conveyor belt of Tory cronies serve only to discredit the honours process".
Leading lights from sport and showbiz to science and charity work are handed honours at Buckingham Palace each year for their service to the nation.
Political names are often included, with billionaire Tory donor David Harding handed a knighthood in the 2022 New Year Honours.
King Charles' first New Years' Honours list is due to be published next week.
The selection process for honours, conducted by 10 committees, is shrouded in secrecy.
Sir Vernon Ellis, who served as the Chair of the Arts and Media Honours Committee between 2012 and 2015, said he pushed back against a nomination for a Tory donor during David Cameron's premiership.
“I felt that if he was given the honour, it would bring the honours into a bit of disrepute because people would say how can he possibly deserve this honour when in this other field there was so much kind of going on and noise and some of that was at his door, right or wrong," he told the programme.
He described an exchange with the-then Cabinet Secretary, the late Jeremy Heywood, after he had resisted the pressure to honour the No10-backed candidate.
“He said ‘you know if you continue your position some things might happen that you don't like, there might be some consequences’. And I said ‘really, what sort of consequences?' He didn't say, except said ‘sometimes, you've just got to be pragmatic".
"I just felt in this particular area you shouldn't do that; you should stick for what's right and not...otherwise it's a slippery slope."
Sir Vernon said the donor in question was blocked but later his three-year term as chair was not renewed.
He said: “My committee was outraged because they saw for what it was - it's just because I had taken the stance...wasn't being renewed.
"The next time I saw Jeremy Heywood I said, 'so now I know what you mean by consequences'. He just smiled. I mean, you know, what can he say?
“I don't know what the process was but that was the consequence, and it was quite obvious that was the consequence.”
Pressed on whether he was being punished for standing up to No10, Sir Vernon said: “Oh I don't think there's any question about it.”
He said he believed Sir Jeremy's words had been a well-meant warning rather than a threat.
Lady Suzanne Heywood, Jeremy Heywood’s widow, told Channel 4 News the allegations against her husband were "baseless".
Waheed Saleem, who was appointed to the Community and Voluntary Services Honours Committee in 2019, said he had also come under pressure to approve Downing Street's candidates.
The former Police and Crime Commissioner who said: “So there was subtle pressure, if I want to put it that way, to ensure that these nominations were pushed through."
He claimed that rejected nominations were "continuously put back to the committee until the right answer came along", adding: "So there were these subtle hints about these nominations, because of their links to No 10, should be put through for the high honours.
“We actually did a push back. But it was very interesting how those names were continuously being put forward, until the right answer was given. And that's the politicisation and the political influence that had occurred in the committee. And that's wrong.”
He was later told his place on the committee was not being renewed, despite other members being handed another term.
Mr Saleem said: "I think there's a perception that if you don't toe the line then you're no longer required."
Dame Louise Casey, a current member of the process, warned the Cabinet Office about encroaching politicisation.
“It’s no secret I’ve struggled with the politicalisation of the honours and especially with the last incumbents of No10," she said in a letter.
“I know balancing a demanding No10 with many other pressures is hard, but I also owe it to myself to say when I think something is not right.”
Deputy Labour leader Angela Rayner told the Mirror: "These underhand attempts to game the system to reward a conveyor belt of Tory cronies serve only to discredit the honours process.
"The Conservatives are yet again putting their party interest before the public interest. Labour will turn the page on years of Tory sleaze with our plan to restore standards in public life."
Lib Dem Cabinet Office spokesperson Christine Jardine said: "Rishi Sunak must investigate these allegations - and commit to denying his predecessors, Johnson and Truss, their own honours lists.
“They should not be allowed to reward cronies with gongs."
The Cabinet Office said: "The process for selecting honours is based on merit and approved by committees which are made up of independent members.
"Political awards are a tiny number compared to the overall amount of honours granted.
"Members are appointed for three-year terms and terms can be extended by mutual consent."
