The row over the former Tory leader's resignation honours list escalated on Monday as Mr Sunak said Mr Johnson wanted him "to do something I wasn't prepared to do".

He said this was "to either overrule the Holac [House of Lords Appointments] committee or make promises to people".

Politics Live: Boris Johnson 'asked me to do something I wasn't prepared to do'

Mr Johnson hit back hours later with a fiery statement denying this was the case.

He said: "Rishi Sunak is talking rubbish. To honour these peerages it was not necessary to overrule Holac - but simply to ask them to renew their vetting, which was a mere formality."

Mr Johnson was left furious after some of his political allies - Nadine Dorries, Alok Sharma and Nigel Adams - were not given the peerages he nominated them for.

The appointments were blocked by the House of Lords Appointments Commission (Holac), which confirmed it had taken eight people off Mr Johnson's list.

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The former prime minister was said to be angry after Mr Sunak - who then reviews the list - refused to reinstate his nominations or consider nominating them later on, with Holac not wanting sitting MPs to be put in the Lords.

Allies in the Johnson camp accused the prime minister of "secretly blocking" the peerages - something Downing Street has strenuously denied.

Speaking from London Tech Week earlier on Monday, Mr Sunak said: "Look, when it comes to honours and Boris Johnson.

"Boris Johnson asked me to do something I wasn't prepared to do because I didn't think it was right.

"That was to either overrule the Holac committee or to make promises with people.

"I wasn't prepared to do that - as I said, I didn't think it was right.

"And if people don't like that, then tough."

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Boris Johnson 'asked me to do something I wasn't prepared to do' - Rishi Sunak

His answer was met with a smattering of applause from the crowd.

Mr Sunak's comments were the first public statement he has made on the matter since Mr Johnson dramatically resigned on Friday, just hours after his resignation honours list was published.

'Pathetic playground antics'

Labour MP Chris Bryant, chair of the standards committee, accused the pair of "playground antics" amid the escalating war of words.

He tweeted: "Purely puerile was how I described Johnson's hissy fit resignation. I hadn't thought it would be followed by pathetic playground antics by both Sunak and Johnson arguing over who's lying and who started it."

Downing Street has since defended Mr Sunak's remarks.

Asked whether the prime minister regrets his comments and getting into a public row with his predecessor, his spokesman told reporters: "No. As I say, he was asked a direct question. He gave a clear answer."

Mr Johnson quit as an MP for Uxbridge and South Ruislip on Friday evening over a report from the Privileges Committee, which was investigating whether he lied to MPs about lockdown parties in Downing Street.

As well as Mr Johnson, Ms Dorries and Mr Adams have announced their intention to quit as MPs imminently.

The Johnson camp triggering three by-elections for a prime minister struggling in the polls has not been viewed kindly within Downing Street.

The government is insisting it followed the precedent of accepting Holac's judgements when it comes to nominating people for peerages.

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One ally of Mr Johnson has accused Mr Sunak of "secretly" blocking the peerages for Ms Dorries, Mr Adams and Mr Sharma.

They claimed the current prime minister "refused to ask for them to undergo basic checks that could have taken only a few weeks or even days.

"That is how he kept them off the list - without telling Boris Johnson."

Sky News has asked for evidence to show Downing Street blocked the appointments.

The prime minister's spokesperson said it was "entirely untrue" that anyone from within Number 10 "attempted to remove or change or alter" the list of honours.