On Sunday, Mrs Johnson’s spokeswoman dismissed the claims as a “brutal briefing campaign against her by enemies of her husband”.

“This is just the latest attempt by bitter ex-officials to discredit her,” the spokeswoman said.

“She is a private individual who plays no role in Government.”

Mrs Johnson is known to have fallen out with a number of Mr Johnson’s advisers, including his former chief aide Dominic Cummings.

On Sunday she was also defended by Kwasi Kwarteng, the Business Secretary, who said the ire aimed at her was “interesting”.

“The reportage that somehow she’s got undue influence, I don’t think that’s true,” he said.

“The Prime Minister has been in politics for 25 years and has a pretty strong set of ideas.”

Sarah Vine, who recently separated from Michael Gove, said claims about Mrs Johnson’s role in Downing Street were sexist.

“The trouble is, it’s always the easiest thing to do to blame the woman and the truth is far more complicated than that,” she told the BBC.

“If Boris Johnson has given Carrie too much access or too much leeway, that’s sort of his fault. He is the person in charge. He is the Prime Minister.”

She added: “The way that she’s being portrayed as this… I know that the nickname Carrie Antoinette is witty and a good pun and we all love a good pun, but I just don’t think her head deserves to be on the block in this way.”

‘Political slut shaming’

Ms Vine said that attacks on Mrs Johnson were “the equivalent of political slut shaming”.

In Lord Ashcroft’s book, John Whittingdale the former cabinet minister who Mrs Johnson previously worked for, said the influence she was said to have was inaccurate.

“Yes, I’m sure Boris and Carrie discuss things in a way that previous spouses would not, because they were much less political,” he said. “Samantha Cameron had little interest in politics. Philip May didn’t have a great knowledge of politics.

“This is the first time the PM’s wife has been a committed political activist and had knowledge and experience of working in politics, so of course it’s going to be talked about. But she’s very good. She advised me for 15 months, so I know she’s good,” he is reported to have said.

He added: “Carrie gets a tough time. It upsets her and I feel sorry for her. It’s a pretty lonely existence. I think they’ve struggled. She doesn’t see as much of Boris as she’d like because he’s trying to run the country.’