Scotland Yard has been criticised by legal experts and Tory MPs for urging Sue Gray to limit the publication of her investigation into allegations of lockdown-breaking parties in No 10.

The Metropolitan Police asked the senior civil servant to make only “minimal reference” to events now subject to a criminal investigation, throwing her report into disarray and potentially buying more time for Boris Johnson as he faces a threat to his leadership.

The force argued the constraints on the Cabinet Office report are necessary to “avoid any prejudice to our investigation”, meaning it faces being watered down or a lengthy delay.

Ken Macdonald, the former director of public prosecutions (DPP), said the move seems “disproportionate” in the face of “very powerful” public interest in the report’s swift publication.

Veteran Tory MP Sir Roger Gale, one of the Conservatives to call for Mr Johnson’s resignation, described it as a “farce” which could buy more time for the “lame duck” Prime Minister.

Opposition politicians warned of a “stitch-up” amid growing calls for the official report into potential Covid breaches in Downing Street and wider Government to be published in full, with it having the potential to trigger a vote of no confidence in Mr Johnson.

In a statement on Friday morning, Scotland Yard said: “For the events the Met is investigating, we asked for minimal reference to be made in the Cabinet Office report.

“The Met did not ask for any limitations on other events in the report, or for the report to be delayed, but we have had ongoing contact with the Cabinet Office, including on the content of the report, to avoid any prejudice to our investigation.”

The statement indicates Ms Gray will either have to make significant changes to her report before publication or delay it until after the police inquiry concludes.

Lord Macdonald said there is a “very powerful public interest in the speedy publication” of the Gray report, arguing that although it could “tip off” potential suspects or witnesses, they are likely to be issued with fixed penalty notices not requiring a trial.

Cressida Dick
Metropolitan Police Commissioner Dame Cressida Dick’s officers have opened a criminal probe (Victoria Jones/PA)

“I very much doubt that anything that Sue Gray says is going to come as any great surprise to any of the protagonists so it’s all a bit of a mystery,” the crossbencher told BBC Radio 4’s the World at One programme.

He conceded that if she found, for example, the “co-ordinated deletion of emails or text messages, this could raise the stakes” requiring the police to have more space.

“But absent of that sort of factor – and that’s pure speculation – this does seem to be a very cautious, perhaps overly cautious, move by the Met in the face of a very powerful countervailing public interest for publication,” the peer continued.

“Unless there is some other more serious conduct in play here that we’re not aware of, I do think the police approach this morning has been surprising and in many ways quite unhelpful.

“The risk of the police intervention this morning is that this leaves things hanging in the air for weeks and months and that seems obviously not to be in the public interest.”

Rather than the statement indicating an escalation of the investigation, the PA news agency understood officers were looking into possible breaches of Covid rules that may warrant fixed penalty notices, with the Met’s concerns centring on the ability of officers to effectively investigate.

Sources close to the Gray inquiry have previously indicated she was concerned about the prospect of releasing a report that was shorn of some of its key findings, raising the likelihood of a significant delay.

Officers have not confirmed how many events they are investigating, but reports have suggested it could be as high as eight.

Conservative MP Sir Christopher Chope accused the Met of “usurping its position by seeking to interfere in the affairs of state”.

Raising a point of order in the Commons, he said: “There is no reason for the Metropolitan Police to be able to require Sue Gray not to issue her report in an unamended way for the benefit of the Prime Minister who ordered that report, and for this House, which is eager to see that report.”

His colleague Sir Roger described the police intervention as “ridiculous”, saying: “Unless there is a legal barrier to Sue Gray publishing her report then I believe that it should be published now and in full.”

The Tory argued the soaring cost of living and Russian aggression towards Ukraine require Mr Johnson’s “full and undivided attention”, but instead he is “a lame duck Prime Minister that is soldiering on”.

Government minister Chris Philp said “between Sue Gray’s report and the police investigation, everything will be fully covered”, insisting to broadcasters that “the Government aren’t interfering with it”.

Labour leader Sir Keir Starmer, another former DPP, gave a measured response, calling for the full report to be published “as soon as possible” but conceding that “any issues of prejudice have got to be worked through”.

Fran Hall, whose husband served in the police for more than three decades before dying with coronavirus, accused the Met of letting bereaved families down as the Gray inquiry becomes “a circus”.

Sue Gray
Sue Gray’s report remains awaited (Gov.uk/PA)

The spokeswoman for the Covid-19 Bereaved Families for Justice said: “It’s incredibly painful and they have let families like mine down. My husband was completely committed to justice, and he would have been appalled by this.”

Liberal Democrat leader Sir Ed Davey said: “A stitch-up between the Met leadership and No 10 will damage our politics for generations, and it looks like it is happening right in front of our eyes.”

SNP Westminster leader Ian Blackford called for the report to be published “in full and undoctored without further delay”.

“People are understandably concerned that this increasingly looks like a cover-up,” he added.

Further legal experts including Adam Wagner, a human rights barrister who is an expert on Covid regulations, questioned how a “factual” inquiry could possibly prejudice a criminal investigation.

Nazir Afzal, a former chief Crown prosecutor for the North West, said: “This is absolute nonsense from the Met Police. A purely factual report by Sue Gray cannot possibly prejudice a police investigation.”

Downing Street said it had not had any conversations with the Met or the Cabinet office over what can be published.

The official inquiry has been long-awaited but its publication was thrown into disarray on Tuesday when Met Police Commissioner Dame Cressida Dick, who had long resisted calls to investigate, announced her officers had opened a criminal probe.

It was understood Ms Gray’s team were still working on the investigation while in contact with the Met.

So far seven Tory MPs have publicly called for Mr Johnson to quit, but others are believed to have done so privately in letters to the chairman of the Conservatives’ 1922 Committee.

If the number of letters received by Sir Graham Brady hits 54, representing 15% of all Tory MPs, then a vote of no confidence in the Prime Minister’s leadership is triggered.

Mr Johnson would have to then win the support of half of Conservative MPs in order to stay in No 10.