Boris Johnson's policy chief has quit in protest over the Prime Minister's Jimmy Savile slur on Keir Starmer.
Munira Mirza told the PM "it was wrong" for him to imply the Labour leader was "personally responsible" for not prosecuting the paedophile, the Spectator reports.
Ms Mirza said she urged Mr Johnson to apologise today, in a letter to the PM, but "despite my urging you did not apologise for the misleading impression you gave."
"I appreciate that our political culture is not forgiving when people say sorry, but regardless, it is the right thing to do," she told the Prime Minister.
"It is not too late for you but, I'm sorry to say, it is too late for me."
The Prime Minister lashed out at Mr Starmer on Monday during a Commons debate on lockdown breaking parties in Downing Street, after Sue Gray published her redacted "update" report.
The PM was “strongly advised” not to make the Savile reference, according to the Financial Times - which quoted one Tory MP branding it “totally outrageous”.
Mr Starmer led the Crown Prosecution Service when it decided not to prosecute Savile in 2009 due to insufficient evidence, a decision it later apologised for.
But the Full Fact website investigated in 2020 and found it had never actually been suggested that Sir Keir was personally involved in the decision.
Victims of Savile have expressed their "disgust" and urged the PM to apologise.
Richard Scorer, head of abuse and public inquiries at law firm Slater and Gordon told the Mirror many of the victims he represented feel the Prime Minister is "using" them to climb out of a "political hole".
A Number 10 spokesperson responded to her resignation and said: "We are very sorry Munira has left No 10 and are grateful for her service and contribution to government.
"Andrew Griffith has been appointed Head of the No 10 Policy Unit and will work across government and with MPs as we continue to deliver and expand on our ambitious policy agenda."
Ms Mirza was once described as one of five women who had the most influence on Mr Johnson's life.
In a letter to the Prime Minister, Ms Mirza 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."
Responding to her resignation, Dominic Cummings said: "Moral courage from Munira who has done her best to make progress with a professional team throughout the horror since 11/20.
"It's also an unmistakeable signal the bunker is collapsing and *this PM is finished*."
Asked if the PM believed Keir Starmer had acted improperly over Jimmy Savile, the PM's press secretary said: "He was simply pointing out Sir Keir Starmer's record as leader.
"You've got what the PM said today which is that in 2013 Starmer apologised and took full responsibility for what happened on his watch and that was the right thing to do."
Asked if the PM got his information from conspiracy theorists, the press secretary said: "No... it is all entirely a matter of public record."
Ms Mirza has been a huge asset to the PM's journey from City Hall through to Downing Street.
She established the controversial Commission on Race and Ethnic Disparities in the wake of international protests in the wake of George Floyd's death.
