Boris Johnson aide Munira Mirza quits with damning letter over Jimmy Savile row

In a fresh blow to the Prime Minister, his long-term ally and adviser Munira Mirza resigned in outrage at his “inappropriate and partisan reference to a horrendous case of child sex abuse”.

News of her resignation came just hours after Mr Johnson had backtracked on his claim by admitting Sir Keir “had nothing to do personally” with the decision not to pursue a prosecution against Savile.

But Ms Mirza, who has worked with Mr Johnson for more than a decade, said the Prime Minister had not properly apologised.

The Spectator magazine reported her resignation letter to the Prime Minister 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.

“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.”

She ended the letter by calling on Mr Johnson to issue an apology.

"Even now, I hope you find it in yourself to apologise for a grave error of judgement made under huge pressure. I appreciate that our political culture is not forgiving when people say sorry, but regardless, it is the right thing to do. It is not too late for you but, I’m sorry to say, it is too late for me."

The controversy began on Monday when Mr Johnson claimed in Parliament that Sir Keir had “spent most of his time prosecuting journalists and failing to prosecute Jimmy Savile” during his time in charge of the Crown Prosecution Service. It sparked a furious reaction, including from victims of Savile and the Prime Minister was accused of “weaponising” their experiences for political gain.

Mr Johnson told the Sun he believed his comments were “fairly accurate” and doubled down on the claim on Wednesday during Prime Minister’s Questions, highlighting a 2013 apology from Sir Keir for the failures of the CPS in the matter.

There is no evidence that Sir Keir had any personal role in the failure to prosecute the man who was one of Britain’s most egregious sex offenders before his death in 2011.

The Labour leader accused Mr Johnson of “parroting the conspiracy theories of violent fascists to try to score cheap political points”.

Today Mr Johnson said he wanted to “clarify” his remarks because a lot of people “got very hot under the collar” amid anger from his own MPs and lawyers representing Savile victims.

Speaking to broadcasters in Blackpool, the Prime Minister said: “I want to be very clear about this because a lot of people have got very hot under the collar, and I understand why.

“Let’s be absolutely clear, I’m talking not about the Leader of the Opposition’s personal record when he was DPP and I totally understand that he had nothing to do personally with those decisions. 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.”

A spokesman said Downing Street was “very sorry” to see Munira Mirza quit as Arundel and South Downs MP Andrew Griffith was appointed as her replacement.

He said: “We are very sorry Munira has left No 10 and are grateful for her service and contribution to Government.

“Andrew Griffith MP 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.”

The resignation of one of his most loyal allies, who has worked with him for more than a decade, further weakens the Prime Minister as he battles to remain leader.

The Tory revolt against Mr Johnson over allegations of lockdown-breaching parties in No 10 was growing, with 13 Conservative MPs calling for his resignation.

Mr Johnson once praised Ms Mirza as a “brilliant thinker” and listed her as one of the five women who had influenced and inspired him the most.

Dominic Cummings, the former chief aide to No 10 who is agitating for the Prime Minister’s removal, said her resignation is an “unmistakable signal the bunker is collapsing”, adding that the “PM is finished”.

Mr Johnson's partial retreat over the remarks came after Cabinet ministers were sent out to defend Mr Johnson’s deployment of the conspiracy theory said to have been spread by supporters of the far-right.

But Tory critics of Mr Johnson deploying the falsehood while his leadership is imperilled included former minister Tobias Ellwood and senior MPs Simon Hoare and Sir Charles Walker.

Scottish First Minister Nicola Sturgeon compared Mr Johnson to former US president Donald Trump spreading “fake news”.

Commons Speaker Sir Lindsay Hoyle also rebuked Mr Johnson, saying he was “far from satisfied that the comments in question were appropriate on this occasion”.

Lawyer Richard Scorer, who represented many of Savile’s victims, had said said: “Victims of Savile I represented and have spoken with today are all disgusted by Boris Johnson’s comments.

“They’ve told me they want him to withdraw them and apologise. I urge Johnson to do that right away.

“Weaponising their suffering to get out of a political hole is disgraceful.”