Boris Johnson on Thursday awaited a report into lockdown-breaking parties at Downing Street that could determine his future as Britain's prime minister, and rejected new claims that he prioritised pets over people in the chaotic Afghan evacuation.

Senior civil servant Sue Gray had been expected to publish her findings about the "partygate" allegations, which have seen mounting calls for Johnson to quit.

But its publication has been put on hold, due to the Metropolitan Police launching its own probe into the claims that have caused public and political outrage.

Johnson's spokesman said he remained committed to publishing Gray's report in full, but Downing Street had yet to receive a copy.

The government also wants reassurance from London police that it does not "cut across" their investigation, so as not to prejudice any future legal proceedings, the spokesman added.

Downing Street has denied Boris Johnson intervened to secure the evacuation of animals from Kabul as the Tliban seized power
Downing Street has denied Boris Johnson intervened to secure the evacuation of animals from Kabul as the Tliban seized power POOL via AFP / Yui Mok

"We are in no way seeking to block the report," he said.

Government lawyers and human resources officers, along with civil service trades unions, are also reportedly vetting the report.

Johnson has promised to address parliament once Gray's report is out but the prospect of that happening this week was fading.

The prime minister on Thursday was in north Wales, while no further government statements were scheduled in the House of Commons.

On Friday, most MPs will be back in their home constituencies. The few left in London will be debating only "private members bills" -- personal initiatives that stand little chance of legislative success.

The issue adds to questions about his truthfulness after a scandal about lockdown-breaking parties
The issue adds to questions about his truthfulness after a scandal about lockdown-breaking parties POOL via AFP / Charlotte Graham

"What I hope people understand is that while we wait for all that to go on, you've got to get on, and the government is getting on with our work," Johnson told reporters.

There has been a steady drip of revelations about Downing Street gatherings that broke social distancing restrictions the government set for the public.

Political opponents have accused Johnson of misleading parliament by insisting all the legally binding rules were complied with and that the events were work-related.

Boris Johnson's potential challengers
Boris Johnson's potential challengers AFP / Jonathan WALTER

Newly released foreign ministry emails about the Taliban takeover of Afghanistan from August, however, have fuelled further questions about Johnson's truthfulness.

Johnson in December denied insisting on preferential treatment for a British animal charity, Nowzad, run by a media-savvy former Royal Marine, Paul "Pen" Farthing.

But emails released on Wednesday showed diplomats referring to a decision taken by Johnson to evacuate the staff and animals as the Taliban seized Kabul.

Johnson dismissed the new claims in the emails, given to parliament's Foreign Affairs committee by a whistleblower, as "total rhubarb (nonsense)".

The military evacuation -- dubbed Operation Pitting -- managed "an amazing thing to move 15,000 people out of Kabul in the way that we did", he told reporters.

"But I can tell you that the military always prioritised human beings, and that was quite right."

The rushed nature of the evacuation meant thousands of Afghans, who had served Britain in various capacities, were left behind.

The UK has been working since to repatriate those it can reach under Taliban control.

Senior Conservative MP Tom Tugendhat said it was possible that some civil servants had exploited Johnson's name after his wife Carrie -- an animal rights campaigner and friend of Farthing -- reportedly intervened.

Defence Secretary Ben Wallace insisted he had been given no order from the prime minister to prioritise pets.

Johnson's official spokesman told reporters: "The prime minister and Mrs Johnson had no involvement in the Pen Farthing evacuation, as we said previously."

Nevertheless, the Nowzad affair raised anew questions about Johnson's track record on honesty, coming on top of "partygate" and other allegations of government sleaze.

"Somebody is lying about what happened during the events that led up the evacuation of the animals from Afghanistan, and I think it has become increasingly clear that the prime minister story's not credible," Lisa Nandy, a senior MP for the opposition Labour party, said.

"I think it's becoming increasingly clear that you cannot believe a word that our prime minister says," she added.