Ministers in Britain have been warned not to follow Health Secretary Wes Streeting and publish their messages with Peter Mandelson amid a police investigation into alleged misconduct in a public office, it is understood.
In a message last night, the Cabinet Office said members of government should not release material that could be covered by a motion passed in parliament last week.
Meanwhile, Scotland Yard warned that it was "vital due process is followed" so as not to compromise its probe.
It comes after the Mr Streeting, seen by some as a protege of Mr Mandelson, shared a transcript of messages between himself and the former Labour grandee as he sought to distance himself from the peer.
Among the exchanges were concerns expressed by Mr Streeting that the government had "no growth strategy" and that he would be "toast" at the next general election.
In a statement, a Metropolitan Police spokesperson said: "As part of our inquiries, we will review material identified and provided to us by the Cabinet Office to assess whether publication is likely to have a detrimental impact on our investigation or any subsequent prosecution.
"We will work alongside the Cabinet Office to review relevant documents over the weeks ahead. The process to decide which documents should ultimately be published remains a matter for Government and Parliament.
"As we have stated previously, this investigation may be complex but we are focused on a timely and thorough process so that justice is served in this case, or future ones linked to the Epstein files."
Mr Streeting's association with Mr Mandelson has been regarded by some in Westminster as a possible hurdle, should he seek to succeed Keir Starmer as Labour leader.
Speaking to Sky News' Electoral Dysfunction podcast, he said he had shared the messages after a weekend of "smear and innuendo" suggesting he had something to hide.
Government figures are preparing to hand over reams of material to parliament's security watchdog as they face pressure to reveal the extent of what was known about the peer's friendship with Jeffrey Epstein when he was picked for the Washington job last year.
Mr Starmer warned on Friday a "very significant volume of material" - understood to be likely to run into the high tens of thousands - would need to be reviewed.
Following a Commons motion, Downing Street agreed to release all documents relating to Mr Mandelson's appointment, including messages between ministers and senior officials that have the potential to prove embarrassing for the government.
Control over which files can be released into the public domain has been ceded to Parliament's Intelligence and Security Committee (ISC) after a Labour backlash to No 10's initial attempt to add possible exemptions to protect international relations.
The Prime Minister has apologised for his decision to appoint Mr Mandelson but vowed to stay in No 10 to fulfil "my mandate and my responsibility to my country" after surviving renewed calls for his resignation from members of his party, including Scottish Labour leader Anas Sarwar.
Starmer says will 'never walk away from mandate'
Meanwhile, Mr Starmer said he would never walk away from his mandate, amid mounting pressure on his leadership over Mr Mandelson's appointment.
"I will never walk away from the mandate that I was given to change this country," Mr Starmer said.
"I will never walk away from the people that I'm charged with fighting for, and I will never walk away from the country that I love."
In his first public comments since Labour's Scottish leader Anas Sarwar called for him to quit, Mr Starmer hit out at infighting within the party.
Speaking at an event in Hertfordshire, he said the political "turmoil" would not stop him focusing on tackling cost-of-living pressures and improving opportunities for people from disadvantaged backgrounds.
He said: "I am their Prime Minister, and this is their Government and I will never give up on that fight.
"There are some people in recent days who say the Labour Government should have a different part, a fight with itself, instead of a fight for the millions of people who need us to fight for them.
Mr Starmer chaired a cabinet meeting this morning after surviving renewed calls for his resignation from members of his own party.
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At the political cabinet – without civil servants – Mr Starmer thanked his top team for their support, saying they were "strong and united", a readout of the meeting said.
"The prime minister said that the whole of the Labour Party wants Anas Sarwar to become First Minister (of Scotland) and will fight for a Labour government in Scotland," the readout said.
The routine meeting came a day after his top ministers rallied round him despite Mr Sarwar urging him to step down amid the fallout from the Peter Mandelson controversy.
Mr Sarwar became the most senior Labour figure to call for Mr Starmer to go, citing concern that the "distraction" from Downing Street would harm his party's chances of unseating the SNP in May's Holyrood elections.
But, backed by his cabinet, Mr Starmer issued a defiant response at yesterday evening's meeting of the Parliamentary Labour Party, telling a packed room in Westminster: "I've won every fight I've ever been in."
He said he was "not prepared to walk away" as he received a warm reception from MPs reluctant to join Mr Sarwar in calling for him to quit.
The lack of a concerted effort by MPs to depose Mr Starmer suggests the immediate danger may have passed.
Conservative leader Kemi Badenoch, writing in the Daily Telegraph, said Mr Starmer should resign as he had "proved incapable of doing the things a prime minister needs to do".
