Sky News understands from three government sources that, as of Wednesday afternoon, the report is yet to have been sent to Number 10 as senior civil servant Ms Gray is running it past lawyers, HR and the Metropolitan Police to make sure the document can be published in full.

This requires a delicate checking process to be carried out due to the duty of care there is to Downing Street staff who may be implicated in the report.

PM braces for release of 'partygate' report - politics live

The prime minister has vowed to make a statement and answer questions in the House of Commons after the Gray report has been made public.

But with the House of Commons having adjourned for the day almost three hours earlier than scheduled before 5pm, any consideration of the findings in the chamber by MPs will now have to wait until Thursday at earliest.

Meanwhile, earlier today, the prime minister failed to explicitly commit to publishing the full report once the findings of the long-awaited inquiry are finally received by Downing Street.

Asked at PMQs by Labour leader Sir Keir Starmer if he will release the entirety of Ms Gray's report, the prime minister replied: "We've got to leave the report to the independent investigator, as he knows, of course when I receive it, of course, I will do exactly what I said."

Government's 'intention' to 'publish it as received'

Questioning the PM, Sir Keir noted the ministerial code states that ministers who knowingly mislead parliament are expected to offer their resignation

"Does the prime minister believe that applies to him?"

Mr Johnson replied: "Of course, but let me tell the House that I think he is inviting a question about an investigation which is - as you know, Mr Speaker, I cannot comment - and which he, as a lawyer, will know that I can't comment on."

Explainer: Who is party investigator Sue Gray?

Sir Keir asked Mr Johnson whether, given he acknowledged the ministerial code applies to him, he would be resigning for misleading parliament over the partygate furore.

"No," the PM replied.

Mr Johnson's spokesman said it is the government's "intention" to "publish it as received".

'Security issues' with publishing report

Speaking to Kay Burley earlier on Wednesday, Foreign Secretary Liz Truss said the government would release the "findings" from the Cabinet Office inquiry.

However, she said there could be "security issues" which mean parts of it are "problematic to publish".

Ms Truss also said Boris Johnson has her "100% support" as the prime minister faces calls, including from some of his Conservative MPs, to resign over the partygate revelations.

The foreign secretary said she did not attend any parties in Downing Street and was not invited to any.

The crisis engulfing the PM deepened on Tuesday when the Metropolitan Police announced it is investigating a "number of events" in Downing Street and across Whitehall for potential breaches of COVID-19 regulations.

On Wednesday afternoon, Conservative MP Mark Logan told Sky News a "change to the infrastructure around the prime minister" was needed, adding: "But I believe if he digs - and when he digs deep - is that we can make that change and we can get over what has been a difficult couple of weeks for the government and for the country."

Read more: What could Sue Gray's inquiry into No10 parties mean for PM and who decides what happens next?

Uncertainty over report's publication

Expectations had been raised that Mr Johnson would address the Gray report's findings in the Commons on Wednesday lunchtime.

On Tuesday afternoon, it was understood that Number 10 would publish the report compiled around midday and then the PM would make a statement in the Commons after PMQs.

But the timing still remains unclear.

It is thought many MPs are likely to be away from Westminster on Thursday, instead attending ceremonies to mark Holocaust Memorial Day in their constituencies.

Opposition parties had voiced concern on Tuesday that, if published today, they would not be given sufficient time to read the document before any potential statement from the PM later in the day.

Sky News understands Ms Gray wants the report to be published in full and it will cover all the alleged events, not just those the police are not investigating.

Labour has called for the report to be published "in full" - with Sir Keir saying anything less would amount to a "cover-up".

The party could try and use parliamentary procedures to try and force the publication of the document in full.

Such an attempt could take the form of a "humble address", effectively a message to the Queen demanding the publication of papers.

Met Police launch criminal investigation

Metropolitan Police Commissioner Dame Cressida Dick announced on Tuesday that the force was investigating "a number of events" for potential breaches of COVID-19 regulations.

Mr Johnson has welcomed the probe and said it would "help draw a line under matters".

Sources have told Sky News this investigation will take "weeks, not days".

Read more: Which lockdown parties is Sue Gray investigating, and what has Downing Street said about them?

Downing Street has said the PM is willing to be interviewed by police but does not believe he has broken the law.

His spokesman said he was not aware of the police asking to interview Mr Johnson, but "as a rule I'm not going to be getting into individuals who may or may not be involved".

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Photos of No 10 parties show PM next to wine bottles

Legal commentator Joshua Rozenberg told Sky News that if Mr Johnson were to be interviewed under caution he would "clearly be a suspect" as he is suspected of committing a criminal offence.

Mr Johnson's leadership has come under severe pressure amid the ongoing partygate scandal and he could face a vote of no confidence if more than 54 Conservative MPs submit letters of no confidence to the 1922 Committee of backbenchers.

Yesterday evening, it was understood that Ms Gray had received photographs showing Mr Johnson and others close together with wine bottles when COVID rules were in place as part of her investigation.