It comes after Sky News revealed Boris Johnson had met the senior civil servant about the progress of her inquiry.

The BBC reported Ms Gray initiated the meeting "to clarify her intentions" for what would happen once the police investigation concluded and also touched on whether photos from the parties would be revealed to the public.

But a spokesman for the Gray inquiry has disputed this account of events and disagreed with the claim that photos had been discussed at the meeting.

No 10 were swift to respond with a source saying: "The PM did not request the meeting and hasn't tried to influence the outcome in anyway.

"It's rightly for Sue to decide and it's all done independently."

However, the briefing war will only increase the pressure on the PM to explain the meeting with Ms Gray, given the highly anticipated report has repeatedly been described as independent.

Mr Johnson has said he wants to disclose the maximum available information now to get the issue out of the way so would not have pressured her to drop the report, it is claimed.

The pair would not have discussed the judgements that Ms Gray was preparing to come to in the report, according to multiple sources.

But Labour's deputy leader Angela Rayner called on the prime minister to "urgently explain" why the "secret meeting" had taken place.

She said public confidence in the process had already been "depleted", and people "deserve to know the truth".

"This is a Prime Minister incapable of taking responsibility for the rotten culture he has created in Downing Street or of doing the decent thing," she added.

"The Sue Gray report must be published in full and with all accompanying evidence."

Read more: What is the Sue Gray report and what can we expect from the full findings?

Liberal Democrat MP Christine Jardine said: "Any whiff of a stitch-up would make an absolute mockery of the report."

On Thursday, the Metropolitan Police confirmed they had ended their investigation into lockdown-breaking parties in Downing Street and Whitehall, and had given out 126 fines for 83 people.

The £460,000 investigation into the partygate scandal, which has lasted nearly four months, has already resulted in fines for the PM, his wife Carrie Johnson, and Chancellor Rishi Sunak over a birthday gathering for the prime minister.

Sky News understands that Mrs Johnson has also been told there will be no further action against her.

Labour leader Sir Keir Starmer, who has called for Mr Johnson to quit over his fine, said the investigation had shown "industrial scale law breaking in Downing Street... that reflects a culture and the prime minister sets the culture".

The conclusion of the police investigation cleared the way for Ms Gray's report into the parties to be published in full.

A source close to her team said the aim was to publish it as soon as possible, with next week likely.

Sky News understands discussions about whether or not to name senior civil servants who have been awarded fines are ongoing.

Mr Johnson also faces a parliamentary investigation into whether he misled the House of Commons about the parties.