Policy adviser Elena Narozanski is the latest to leave her role, after four senior staff members quit on Thursday.

Mr Johnson attempted to rally staff at a meeting on Friday morning, telling them "change is good".

The PM is battling to save his premiership as Conservative MPs consider whether to oust him over lockdown parties in Downing Street.

A No 10 spokesman confirmed the PM quoted The Lion King character Rafiki, telling them "change is good", at a meeting with his team and acknowledged it was a "challenging time".

They added that Mr Johnson "reflected on the privilege of working in No 10" and "thanked those who are leaving for their contribution alongside the whole team for their work".

On Friday morning, backbencher Huw Merriman told BBC Radio 4's Today programme the PM should "shape up or ship out".

But Energy Minister Greg Hands told BBC Breakfast the resignations came after Mr Johnson "made it clear there would be a shake-up" of the Downing Street operation, following criticism from senior civil servant Sue Gray in her report on rule-breaking parties.

When asked about Ms Gray's findings, Health Secretary Sajid Javid said the prime minister had "started making changes" and supported his leadership.

Three of the departed aides were caught up in the lockdown parties row, including senior civil servant Martin Reynolds, who sent out an invitation to a "bring your own booze" party.

But policy chief Munira Mirza quit over the PM's false claim that Labour leader Sir Keir failed to prosecute Savile when he was director of public prosecutions, and his refusal to apologise.

In a scathing resignation letter, Ms Mirza - who worked alongside the PM for 14 years - described the his comments about Savile as "scurrilous".

Chancellor Rishi Sunak publicly distanced himself from the PM's original comment, saying: "Being honest, I wouldn't have said it."

And asked if Mr Johnson should apologise, he said: "That's for the prime minister to decide."

Education policy adviser Elena Narozanski - a keen amateur boxer - is the latest No 10 aide to resign

The director of communications, Jack Doyle, confirmed his exit shortly after the departure of Ms Mirza.

Mr Doyle told staff that "recent weeks have taken a terrible toll on my family life", but that he had always intended to leave after two years.

A statement from a No 10 spokeswoman said chief of staff Dan Rosenfield had offered his resignation to the prime minister earlier on Thursday, but would stay on while his successor was found.

And Mr Reynolds - the prime minister's principal private secretary - will do the same, but then return to a role at the Foreign Office.

Ms Narozanski - who quit on Friday morning - is understood to have been loyal to Ms Mirza.

Ms Mirza's resignation was the "most significant", Labour's shadow secretary for climate change Ed Miliband told the BBC.

Condemning the "terrible slur" against Sir Keir, Mr Miliband said the PM had become "a stain on our politics" and called on Tory MPs to oust him.

Sunak's stance

Rishi Sunak is a politician who likes to stick to the script - and choose his words carefully.

As the favourite to take over from Boris Johnson - the chancellor knows any criticism of the prime minister is highly significant.

So his decision on Thursday to very publicly distance himself from Mr Johnson made many in Westminster sit up and take notice.

At a press conference, Mr Sunak made it perfectly clear he disagreed with Mr Johnson's comments about Sir Keir's time as director of public prosecutions.

The prime minister said earlier this week that Sir Keir had failed to prosecute Savile - despite the Labour leader not being involved in that decision. You can read a Reality Check here.

Asked about the PM's controversial comments, the chancellor replied: "I wouldn't have said that."

There are further comments in The Sun this morning too, making light of the controversy over parties in Downing Street.

"We've always been the party of sound money, we'll always continue to be on my watch, and that's the only kind of party I'm interested in," writes Mr Sunak.

The chancellor has always insisted he works well with the PM.

But at a time when Mr Johnson is under pressure over his judgement, even mild mannered criticism from Mr Sunak will lead many to question what the chancellor is up to.

Letters of no confidence

The resignations of aides come as backbench unrest is growing within the Conservative Party.

The BBC is aware of 17 Tory MPs who have submitted letters of no confidence in the prime minister - 54 are needed to trigger a leadership contest.

Many have cited the PM's participation in parties with staff in No 10 during lockdowns as their motivation to challenge Mr Johnson.

These gatherings included a "bring your own booze" garden party in May 2020 - the email invite to which was sent by Mr Reynolds.

The Metropolitan Police has launched an investigation into 12 of the parties and a full report by Ms Gray is expected to be published afterwards.

Who are the aides who resigned?

The head of policy at No 10, Munira Mirza worked for Boris Johnson for 14 years, including when he was mayor of London, and was seen as one of his most trusted advisers.

Jack Doyle worked as a Daily Mail journalist before joining Downing Street. He is reported to have attended one of the Christmas gatherings in December 2020, where he thanked staff for their work.

Martin Reynolds is a civil servant and worked as Mr Johnson's Principal Private Secretary. In that role, he headed up the PM's private office. He is responsible for sending an email invitation to staff inviting them to socially distanced drinks in the No 10 garden in May 2020.

Dan Rosenfield joined Number 10 as chief of staff in January 2021, and had worked in the Treasury for former chancellors Alistair Darling and George Osborne.

Elena Narozanski - Education policy specialist. Former adviser to Michael Gove and Theresa May, who headed the New Schools for London programme, when Mr Johnson was mayor. Amateur boxer in her spare time.

Speaking to Channel 5 News after Ms Mirza quit - but before the news of the other resignations was made public - the prime minister said he was "sorry to lose Munira".

But asked about her conclusion that his remarks about Sir Keir had been "inappropriate and partisan", Mr Johnson replied: "Well, I don't agree with that."

He said: "No-one is commenting, least of all me, about the personal involvement of the leader of the opposition in the handling of that case.

"All that I've said is that the leader of the opposition apologised for the CPS's handling of that issue during his tenure and that's all frankly that needs to be said on that matter."