The Prime Minister gave a speech during a crowded departure for a senior official last November when the country was in lockdown for the second time, the Mirror reports.
Members of his best team then threw their own party in Downing Street a few days before Christmas, when London was under Tier 3 restrictions.
Officials have reportedly spilled glasses of wine during a Christmas quiz and a secret Santa Claus while the rest of the country has been ordered to stay home.
About “40 or 50” people would have been crammed “play by play” into a medium sized venue number 10 for each of the two events.
“It was a Covid nightmare,” a source said.
It comes after chief health officer Dr Jenny Harries warned people should cut back on unnecessary social gatherings during the holiday season to curb future outbreaks of Covid.
But Mr Johnson today dismissed the idea that festive parties should be done away with, adding: ‘We don’t want people to cancel such events. “
In explosive revelations, a source told the Mirror that there had been “numerous social gatherings” in Downing Street last year as the public faced restrictions.
They even claimed there were “always parties” in the apartment the Prime Minister shares with his wife, adding “Carrie is addicted to it.”
There were also allegations of a third, smaller rally on November 13, the night Dominic Cummings walked out of No 10, “where they were all in full plaster.”
Another source claimed: “As senior officials urged caution and there was a message to the public, the PM gave the impression that he could be very relaxed at No 10.
“He closed his eyes or, on some occasions, looked after himself while everyone was locked up.”
The official No.10 Staff Christmas Party was canceled and officials reportedly took a Zoom quiz instead.
But the departure still took place on November 27 while the unofficial Christmas party, which the Prime Minister did not attend, took place on December 18.
A legal expert said the events could even have been punishable by a fine of £ 10,000.
Downing Street did not deny the claims, but a spokesperson said: “The rules of Covid have been followed at all times. “
A spokeswoman for Ms Johnson denied hosting parties at the apartment while restrictions were in place, adding: ‘This is total nonsense.
“Ms Johnson has always followed the rules of the coronavirus and it is categorically wrong to suggest otherwise. “
Last November, Mr Johnson plunged England into its second nationwide lockdown for four weeks with people being asked to work from home and all indoor socialization banned.
London entered Tier 2 restrictions the following month – which prohibited households from mingling indoors.
The city – which had the highest rates of Covid cases in the country – then moved to Level 3 on December 16, which banned all mixing indoors except in domestic bubbles.
The only possible legal means for either gathering to take place was if it was “reasonably necessary for the work” under the regulations.
Downing Street staff have been rated as key workers throughout the pandemic.
Their offices have been set up to be secure against Covid, with Plexiglas screens between the desks and hand sanitizing stations.
The rule of six was regularly enforced during meetings and the number of people allowed to see the prime minister at any time was strictly limited, while social distancing was in place.
Prime Minister officials worked long hours, often late at night as the government struggled to deal with the pandemic.
However, sources claimed Operation 10 attempted to justify the rallies because the participants all worked in the same building.
One said: “It is difficult to officiate because there is a lot of work going on – every now and then until the wee hours of the morning.
“They generally followed the rules, it was just these events that happened from time to time that drove him. “
But another source suggested that “letting off steam” was no excuse for the scale of the rallies that took place in the run-up to last Christmas.
“Tell that to the doctors, nurses and social workers,” they said.