Rishi Sunak has sought to distance himself from Boris Johnson's Jimmy Savile smear on Sir Keir Starmer, telling a Downing Street press conference: "I wouldn't have said it".
It came after the PM's policy chief handed in her resignation over the remarks, citing Mr Johnson's refusal to apologise for the false accusation that Sir Keir failed to lock up paedophile Savile while he was director of public prosecutions.
During a debate on the Sue Gray partygate report on Monday, Mr Johnson said Sir Keir spent his time as head of the CPS "prosecuting journalists and failing to prosecute Jimmy Savile".
Asked about the comments, Mr Sunak said: "Being honest, I wouldn't have said it and I'm glad the prime minister clarified what he meant."
Social media users said the chancellor was positioning himself for a leadership bid if the prime minister resigns or is removed.
Mr Johnson backtracked on his claim on Thursday, accepting the Labour leader had "nothing to do personally" with a decision not to prosecute the disgraced entertainer.
But the clarification wasn't enough for Mr Johnson's head of policy Munira Mirza who suggested she was forced to resign over the lack of an apology.
In a letter to the prime minister, seen by the Spectator, she said: "I believe it was wrong for you to imply this week that Keir Starmer was personally responsible for allowing Jimmy Savile to escape justice.
"There was no fair or reasonable basis for that assertion. This was not the usual cut and thrust of politics; it was an inappropriate and partisan reference to a horrendous case of child sex abuse.
"You tried to clarify your position today but, despite my urging, you did not apologise for the misleading impression you gave."
The PM had also been urged to apologise by two of his own MPs, Julian Smith and Stephen Hammond.
Ms Mirza, who has spent 14 years working alongside Mr Johnson, added: "You are a better man than many of your detractors will ever understand which is why it is so desperately sad that you let yourself down by making a scurrilous accusation against the Leader of the Opposition."
Mr Johnson, in an interview with Channel 5 News, said he "of course" regrets making the comment after suffering the resignation.
In a statement Downing Street said it is "very sorry Munira has left No 10 and are grateful for her service and contribution to government".
She was swiftly replaced following her departure, with Conservative MP Andrew Griffith announced as head of the prime minister's policy unit.
The prime minister made the accusation on Monday while defending himself over the Sue Gray partygate report which condemned a "failure of leadership" in Number 10 under his watch.
On Thursday, the PM told broadcasters he wanted to "clarify" his remarks because "a lot of people have got very hot under the collar" about the widely debunked claim.
"Let's be absolutely clear, I'm talking not about the Leader of the Opposition's personal record when he was DPP (Director of Public Prosecutions) and I totally understand that he had nothing to do personally with those decisions," Mr Johnson said.
"I was making a point about his responsibility for the organisation as a whole. I really do want to clarify that because it is important."
Sir Keir told ITV's Good Morning Britain that accusation is a "slur, it’s untrue", a conclusion Full Fact came to when it investigated the claim in June 2020.
Mr Johnson's spokesperson previously said the prime minister "stands by" his remarks but it appears that is no longer the case.
Savile died in 2011 aged 84 having never been brought to justice for his crimes. He is now believed to be one of Britain's most prolific sex offenders.
His victims were "appalled" by the prime minister's claim, according to a lawyer who represented several of them.
Richard Scorer told ITV News: "I've spoken to a few of our former clients today and they are universally appalled by this.
"What angers them more than anything else is that idea of Johnson trying to weaponise their suffering in order to get out of a political hole."