Keir Starmer has said he won't hand out resignation honours if he becomes Prime Minister - and he could block inappropriate attempts by Rishi Sunak to honour cronies.
The Labour leader said the tradition was "very hard to justify" and ruled out dishing out gongs on leaving Downing Street if elected.
It is understood that Mr Starmer would decline the opportunity rather than axing resignation honours lists completely.
He said Mr Sunak was wrong to wave through Boris Johnson's list of honours for Partygate pals and allies, which has come under fresh scrutiny after the Mirror published a video of a boozy lockdown bash at Tory HQ which included two people honoured by Mr Johnson.
Shaun Bailey, the former Tory mayoral candidate who was pictured at the event, was handed a peerage, while Ben Mallet, who was awarded an OBE in Mr Johnson's list, appears in the video clutching a glass of wine.
Calls have been mounting for the two men to be stripped of their honours.
Mr Starmer said he does not believe either should receive an honour, and argued that "most" of the public would think it "simply inappropriate" for them to be recognised.
Asked if he would have a resignation honours, Mr Starmer said: "No. There are other opportunities but Tony Blair didn't have a resignation list. It is very hard to justify.
"If it was reserved for people who had given incredible service... perhaps picking out people who had been involved in the development of the vaccine or some other real element of public service... but it is very hard to see how it is justified.
"There are other avenues for that and I think it is easier to be clean about this and say no, I wouldn't do it. Tony Blair didn't do it and I wouldn't do it."
Asked if he would intervene if Mr Sunak's list was stuffed with inappropriate names, Mr Starmer said: "Yes. I think that what Rishi Sunak did was wrong."
MPs will debate whether to endorse the Privileges Committee report into Boris Johnson's Partygate lies, which recommended a 90-day suspension for the disgraced ex-PM, after it found he'd misled Parliament multiple times.
Mr Starmer said the PM should have waited for the results of the probe before pushing through Mr Johnson's honours.
"Whatever the previous conventions, we've never had a situation like this where a previous PM has been found to have lied to Parliament, not once but repeatedly. He has now pretty well been stripped of any involvement in Parliament.
"That is unprecedented.
"Why on earth didn't Rishi Sunak say, 'I'll put your list on one side, former Prime Minister. I will get to it but I am determined to see the findings of the Privileges Committee before I do so.
"'Because if, for example, the Privileges Committee says you lied to Parliament, then I'm not going to put your list through'."
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