Mr Shapps, the energy secretary, told Sky News' Sophy Ridge On Sunday that there were now "different challenges to face" and that Downing Street was "under new management".

He said they were "getting on with the job and getting on with the priorities of this country".

Mr Shapps spoke following Mr Johnson's shock decision to resign as the MP for Uxbridge and South Ruislip on Friday, triggering a by-election in his constituency - a key target for Labour.

The former prime minister announced his decision after receiving the privileges committee report into whether he lied to MPs over partygate - something he branded a "kangaroo court" and "witch hunt".

It came just hours after his resignation honours list had been published, with the names of key allies Nadine Dorries, Sir Alok Sharma and Nigel Adams absent.

Labour accuses PM of losing control - politics latest

In a move that will create a headache for Mr Sunak, Ms Dorries, the former culture secretary, and Mr Adams, a former minister, both announced they would stand down from their seats, creating a hattrick of by-elections at a time when the polls are faring badly for the Tories.

Over the weekend there were reports in The Sunday Times that Mr Johnson believed Mr Sunak had broken a promise to wave through the entire list of honours - a charge Downing Street has denied.

But Mr Shapps insisted Mr Sunak made no changes to the list "at all".

Asked whether he thought Mr Johnson was not fully across the process, he said the former prime minister "occasionally... wouldn't be all over the details".

"Rishi Sunak has not changed, altered, the list in any way," he said.

"In fact, there is a House of Commons appointments commission - or Holac as it is called - which looks at all nominations.

"There is a very long-tested protocol in place where former prime ministers put people up for the House of Lords... and the prime minister who comes in usually passes it on.

"In this particular case, because Number 10 has actually published the details, you can see that Rishi did not change that list at all.

"The House of Commons commission will have made all of those decisions and the prime minister has not intervened in any way."

In a statement announcing his resignation, the former prime minister said a letter from the privileges committee made clear "that they are determined to use the proceedings against me to drive me out of parliament".

Mr Shapps has said he did not agree with Mr Johnson's assessment that the committee's partygate probe was a "witch hunt" and an attempt to reverse Brexit.

"I think far from wanting to undo [Brexit], I think we're in a phase now of using the many benefits of having that extra flexibility," he said.

"What I do believe is that it is very important to elect committees, let them get on with their work," he added.

Mr Johnson's decision to quit has reopened questions of a fresh civil war in the Conservative Party, with a number of his allies criticising the privileges committee.

Former Tory Party chair Sir Jake Berry suggested Mr Johnson had been "forced out" by the "establishment" and "the blob".

Read more:
Boris Johnson's resignation honours list in full
Johnson stands down as MP with immediate effect

"You voted for Brexit - the establishment blocked it," he tweeted. "You voted for Boris Johnson - the establishment has forced him out.

"Who is in charge here… The voters or the blob?"

The resignations of Ms Dorries and Mr Adams prompted fears of a rebellion among Mr Johnson's allies, with his supporters claiming that two more MPs are on "resignation watch".

However, claims by Mr Johnson's camp that up to six more MPs were poised to quit have failed to materialise so far.

Mr Johnson's former communications director Guto Harri - who was made a Commander of the Order of the British Empire in the honours list - said he did not believe there was an "elaborate plot to sort of destabilise and topple Rishi Sunak".

He said the former prime minister is seizing an opportunity to remove himself from politics and "lick his wounds, but also seize new opportunities".

Asked whether he thought Mr Johnson would stage a political comeback, he added: "We can never write him off."