Keir Starmer’s failure to release key Mandelson documents “stinks of a cover up”, Kemi Badenoch has warned. The Prime Minister was accused of suppressing crucial sections of papers relating to the appointment of Lord Peter Mandelson as US ambassador. Critics claimed Sir Keir’s notes on the disgraced peer’s appointment to the UK’s top diplomatic role had been “removed” in the first tranche of documents released this week.

Mrs Badenoch said: “The small batch of Mandelson files that the government has released prove that Starmer has been lying about what he knew from the start. But we still don’t have the full picture. Too many of the documents are missing and it beggars belief that Starmer chose not to comment on all of the submissions which went to him in his Prime Minister’s Red Box.”

Mrs Badenoch said: “The whole thing stinks of a cover up. We need full transparency now.”

Sir Keir on Thursday admitted he made a “mistake” in despatching Mandelson to Washington.

Speaking to reporters at the Atlas Women’s centre in Lisburn, Northern Ireland, he said: “It was me that made a mistake and it’s me that makes the apology to the victims of Epstein, and I do that.”

A document on Mandelson’s scandal-ridden past was presented to Sir Keir, but a section for his comments appears blank in the publicly released files.

Box notes are a crucial part of the Whitehall decision-making process, with the Prime Minister’s steer giving mandarins direction and authority to demand action across government.

The Tory leader joined others in warning that crucial information had been “removed” from the long-awaited documents, which showed Sir Keir was warned about a “general reputation risk” over Mandelson’s relationship with convicted paedophile Jeffrey Epstein before handing him the plumb Washington posting.

Shadow Chancellor of the Duchy of Lancaster Alex Burghart demanded answers on why the government had not released the “actual” memo on the appointment.

He said: “I’ve worked in No10 – advisors and private secretary provide comments and we’d expect the PM to write in his view. All that has been left out – why?”

One former No10 advisor told the Express that the Prime Minister’s views on such a memo were “the most important part of the process”.

Another source familiar with the workings of Downing Street said that Sir Kier’s failure to write his notes “could suggest that he was wary of putting his thoughts in writing for this exact reason”.

But Sir Keir repeatedly told MPs in September that “full due process was followed” during the former Cabinet Minister’s appointment.

Downing Street spinners on Thursday denied there was a “cover up”.

It has been suggested that the Prime Minister chose not write any notes on the document and nothing was redacted.

Sir Keir’s spokesman said: “I refute the suggestion of a cover up. The Government complied fully. I just don’t accept that it’s the case at all.

“There are a range of different ways in which the Prime Minister’s senior team responds to advice.

“The Prime Minister did read the advice but clearly there are lessons to be learned on the wider appointment processes, and the processes that led up to them.”

Speaking to the media for the first time since the publication of the Mandelson documents, Sir Keir said “the release of the information shows what was known”.

He claimed that the Epstein files “led to further questions being asked”.

But he refused to be drawn into more specific comments, and said he could not release more files yet because of an ongoing police investigation into the disgraced peer.

Liberal Democrats demanded that the Labour leader refer himself to ethics tsar Sir Laurie Magnus amid allegations he misled parliament.

Lisa Smart, the Party’s Cabinet Office spokeswoman, said: “This is an appalling scandal that seems to get worse by the day.

“The Prime Minister has not only shown a catastrophic lack of judgment over Mandelson’s appointment. The evidence is mounting that he misled Parliament

“Keir Starmer must refer himself to the independent ethics adviser to determine whether he breached the ministerial code.

“He promised to clean up politics after years of Conservative sleaze and scandal, now he must lead by example.”

The scandal has erupted again after 147 pages of papers were published this week following a rare act of parliament which forced their release.

The papers also laid bare that Mandelson demanded more than half-a-million in severance pay after being given the boot, but was handed £75,000 in what civil servants believed was a win.

Former Chancellor George Osborne said that signing off the payout was “very odd” and added that had it come across his desk he would have said “forget it […] see us in court”.

Files suggest that Mandelson received the speedy payout to avoid “reputational damage” to the government as civil servants feared he would “go public” with his criticism.

Sir Keir’s national security adviser Jonathan Powell described the Mandelson appointment as “weirdly rushed” in one part of the files, with the Blairite-era fixer noting Foreign Office officials “also had reservations around the appointment”.

Further files are expected to be released in the coming weeks after approval from the police and the relevant parliamentary committee.

Critics say the scandal has exposed Sir Keir’s flawed judgement, with calls from opponents for him to step aside.

In those documents, it was made clear that the Prime Minister ignored warnings about Mandelson and pressed ahead to give him the £180,000-a year role.

He lasted just nine months before being ousted in September after further disclosure about the relationship with Epstein emerged.

Lord Mandelson, 72, was arrested on February 23 at his London home on suspicion of misconduct in public office.

He was later released without bail as the police probe continues. He denies wrongdoing.