British Prime Minister Boris Johnson was facing fresh allegations of breaking coronavirus rules, after it emerged staff gathered in No 10 to wish him a happy birthday during the first lockdown.
Downing Street said staff only "gathered briefly" in the cabinet room following a meeting, after a report from ITV News suggested up to 30 people attended.
The broadcaster suggested the Prime Minister's wife, Carrie Johnson, had organised the surprise get-together on the afternoon of 19 June 2020, when indoor social mixing was banned.
A No 10 spokeswoman said: "A group of staff working in No 10 that day gathered briefly in the cabinet room after a meeting to wish the Prime Minister a happy birthday. He was there for less than ten minutes."
ITV news also reported that later that evening family friends were hosted upstairs in Mr Johnson's official residence.
Downing Street said: "This is totally untrue. In line with the rules at the time the Prime Minister hosted a small number of family members outside that evening."
The latest allegation comes as Mr Johnson is facing a make-or-break week for his premiership with his future in No 10 hanging in the balance.
Mr Johnson is braced for the delivery of the Sue Gray report into Downing Street drinking parties during lockdown which could determine his fate.
Many Tory MPs have said they will wait to see the findings before deciding whether to push for a vote of confidence which could see him forced out.
At the same time, he is battling new allegations of Islamophobia after one MP claimed she was told she had been sacked as a junior minister because of concerns about her "Muslimness".
Over the weekend two cabinet ministers - Health Secretary Sajid Javid and Education Secretary Nadhim Zahawi - backed calls by Nusrat Ghani for an inquiry into her treatment.
Ms Ghani said that when she raised the matter with Mr Johnson directly after losing her job in a February 2020 ministerial reshuffle, he told her he could not get involved.
In a sign of the tensions with the party, the Chief Whip Mark Spencer - who admitted speaking to her - angrily denied her claims saying they were "completely false" and "defamatory".
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However it is Ms Gray's report - expected later this week - which poses the gravest and most immediate threat to Mr Johnson's survival in No 10.
The British prime minister is reported to be determined to hang onto his position believing that he has done nothing wrong.
However, he may be left with little choice depending on exactly what Ms Gray, a senior civil servant, finds.
With widespread public anger and collapsing opinion poll ratings for the Conservatives - and for Mr Johnson in particular - many Tory MPs are in a mutinous mood.
Many of the so-called "red wall" MPs - who took traditional Labour seats in the 2019 - are said to fear they now look set to lose them again in the resulting backlash against the party.
A move against Mr Johnson looked to have been put on hold last week with the defection of Bury South MP Christian Wakeford to Labour, causing MPs to rally to the party colours.
However the stay may be only temporary with some in No 10 fearing a flurry of letters to the chairman of the backbench 1922 Committee Graham Brady when the report is published.
Under party rules, once the total reaches 54 - 15% of Tory MPs - Mr Brady must call a vote of confidence in the leader.
While Mr Johnson may win such a vote, it would nevertheless be a further body blow to his already diminished authority, raising questions as to how long he could continue.
The report may also lead to renewed calls for the Metropolitan Police to open a criminal investigation if there is clear evidence that the Covid restrictions in place at the time were breached.
Among the events Ms Gray has been investigating is a "bring your own bottle" do in the Downing Street garden in May 2020 during the first lockdown.
Mr Johnson has admitted he was there but said he thought it was a "work event" - an explanation that was met with widespread derision.
She has also been looking at two staff leaving parties on 16 April last year on the eve of the funeral of the Duke of Edinburgh, which have already seen No 10 apologise to Buckingham Palace.
Over the weekend The Sunday Times reported that Ms Gray's inquiry had been widened to cover claims of parties in Mr Johnson's Downing Street flat which he shares with his wife, Carrie, and their two children.
Meanwhile, The Daily Telegraph reported Ms Gray has been taking detailed testimony from police guarding Downing Street helping her to build a detailed picture of the comings and goings during lockdown.
It remains unclear what form Ms Gray's report will take.
Yesterday, Britain's Deputy Prime Minister Dominic Raab said there would be "full transparency" but declined to commit to publishing the report in full.
"The process for it will be for the prime minister to decide," he said.
Labour said the report must be published "in its entirety with all accompanying evidence".
In a further twist, William Wragg, the senior Tory MP who accused the government whips of attempting to "blackmail" MPs seeking to oust Mr Johnson, will discuss his claims with a Scotland Yard detective early this week.
