The UK's top civil servant has quit amid Keir Starmer's shake-up of No10.

The Prime Minister will appoint a new Cabinet Secretary to replace Sir Chris Wormald shortly.

His exit as head of the civil service comes as the Prime Minister tries to reset his Downing Street operation after controversies surrounding the appointments of Lord Peter Mandelson and Lord Matthew Doyle despite their association with sex offenders.

Sir Chris said: "It has been an honour and a privilege to serve as a civil servant for the past 35 years, and a particular distinction to lead the Service as Cabinet Secretary.

"I want to place on record my sincere thanks to the extraordinary civil servants, public servants, ministers, and advisers I have worked with. Our country is fortunate to have such dedicated individuals devoted to public service, and I wish them every success for the future."

But Sir Keir has faced a Whitehall war over his decision to sack the Cabinet Secretary.

The Prime Minister is set to install Dame Antonia Romeo in the top job.

It comes after the departures of Sir Keir’s chief of staff Morgan McSweeney and communications chief Tim Allan.

Rumours that the Labour leader plans to replace Sir Chris with Dame Antonia , the Home Office permanent secretary, triggered a highly unusual warning by a former top mandarin against “doing the due diligence too late”.

Dame Antonia’s former boss Lord Simon McDonald, ex-permanent secretary at the Foreign Office, said there should be a “full process” to appoint a new Cabinet Secretary and that “needs to start from scratch”.

But Conservative leader Kemi Badenoch has accused the PM of throwing his Cabinet Secretary “under a bus”.

In a letter to the Civil Service Commission, Mrs Badenoch said: “It is hard to escape the conclusion that the Cabinet Secretary is simply the latest person to be thrown under a bus by this Prime Minister.

“It is all the more concerning to be changing Cabinet Secretary in the midst of the ongoing scandal over the appointment of Lord Mandelson and his conduct in office.”

Mrs Badenoch urged the commission to advise Sir Keir to delay the sacking until the disclosure of Government files relating to Lord Mandelson – overseen by the Cabinet Secretary – is complete.

The probe led by the top civil servant into the former UK ambassador to Washington’s contact with paedophile financier Jeffrey Epstein while he was a government minister should also be concluded first, she said.

Dame Antonia was reportedly investigated when she was Britain’s consul general in New York in 2017 over her expenses and claims of bullying, but was later cleared by the Cabinet Office.

A Government source said there was “absolutely no basis for this criticism”.

They said: ⁠”Antonia Romeo is a highly respected permanent secretary with a 25-year record of excellent public service.

A second Government source went further, saying: “This is a desperate attempt from a senior male official whose time has passed but spent their career getting Britain into the mess it finds itself in today.

“A computer says no culture, that cannot challenge the status quo.

“Antonia is a disrupter. She isn’t settled with the status quo.

“She is one of the few senior officials that has always fought against the computer says no culture embedded in the British state.

“In light of the crisis we face as a country, Antonia is exactly the leadership the civil service need to embrace systemic reform to rewire the state, take on vested interest and deliver for the British people.

“The allegations all come from a single grievance made some time ago by a former employee.

“All the allegations were dismissed on the basis there was no case to answer.”