Boris Johnson’s controversial Jimmy Savile attack on Sir Keir Starmer was “perfectly reasonable”, the Business Secretary has claimed.

Kwasi Kwarteng attempted to downplay a Cabinet split over the Prime Minister’s allegation, but his defence was criticised by a fellow Tory.

Gavin Barwell, a Conservative peer who previously served as Theresa May’s chief of staff, branded the debunked Savile claim “a stupid thing” for Mr Johnson to have done.

The PM initially accused Labour leader Sir Keir of having “used his time prosecuting journalists and failing to prosecute Jimmy Savile” when he was head of the Crown Prosecution Service.

The comment was made in the House of Commons as the Prime Minister faced criticism over Downing Street parties during the pandemic.

He later backed down and said he wanted to “clarify” his remarks, claiming he had not been talking about Sir Keir’s “personal record” when he was director of public prosecutions.

Mr Kwarteng was asked whether he would have used the same words as the Prime Minister.

He told Trevor Phillips On Sunday on Sky News: “I think it’s entirely legitimate… it depends what the context was.

“In that context, I think it was perfectly reasonable to mention the fact that Sir Keir had apologised.

“Sir Keir himself apologised on behalf of the organisation that he led about the fact that they failed to prosecute Jimmy Savile.

“So the fact that he apologised suggests that he does at some level bear some responsibility.”

Mr Kwarteng said he was not saying Sir Keir had “personal blame”.

Lord Barwell told the same programme: “Even if you set aside that moral argument, on a purely tactical level it was a stupid thing for the Prime Minister to do.

“Because it’s led to the resignation of one of his key aides, it’s led to more MPs submitting letters of no confidence in him. It’s further destabilised his position.

“The point here is that we know he was given advice not to do that, and went ahead and did it anyway.

“What that tells you is that yes, having the right people around you can help. But ultimately, the culture at Number 10 and the decisions the Government makes come from the top.

“The Prime Minister himself, if he’s going to stay in office, is going to have to change the way he is behaving and running the Government.”

Chancellor Rishi Sunak and Health Secretary Sajid Javid have both indicated they would not have said the remarks, although Mr Kwarteng told T&G on Times Radio: “I don’t think they were criticising the Prime Minister.

“They were making a specific point about what they would have done in the course of a debate, and I don’t think that’s a criticism of anybody.”

One of Mr Johnson’s most loyal aides, Munira Mirza, quit as No 10’s head of policy over his use of the “scurrilous” Savile smear against Sir Keir.

Lawyers representing Savile’s victims have also criticised the Prime Minister.