Boris Johnson had a birthday party during the first lockdown when indoor gatherings were banned, according to reports.
The Prime Minister, born on June 19, celebrated with up to 30 people, including the interior designer who decorated his Number 11 flat Lulu Lytle in 2020, ITV news reports.
At the time of this alleged gathering, social mixing indoors was banned, people could only meet their loved ones outside in groups of up to six people and most schools remained closed to their pupils.
People who lived alone in England and Northern Ireland were able to form a “support bubble” with another household.
Carrie Johnson and Ms Lytle presented Mr Johnson with a cake, as Carrie led staff to sing a chorus of Happy Birthday.
People were not allowed to mix indoors at the time.
What were you doing on June 19th 2020? Email webnews@mirror.co.uk.
Days earlier, Mr Johnson asked the public "to continue to show restraint and respect the rules which are designed to keep us all safe".
Labour Leader Sir Keir Starmer has said it's "yet more evidence" that the Prime Minister Boris Johnson "thinks the rules do not apply to him".
The party was held in the Cabinet Room, after Mr Johnson returned from a visit to a school in Hertfordshire.
A group of schoolchildren from Bovingdon School in Hertfordshire had sung Happy Birthday to the PM before this party. They were all standing outside in the school playground.
A spokesman for Lulu Lytle said: "Lulu was present in Downing Street on 19 June working on the refurbishment.
"Lulu was not invited to any birthday celebrations for the prime minister as a guest. Lulu entered the cabinet room briefly as requested, while waiting to speak with the Prime Minister."
In response to the allegations Number 10 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.”
A Number 10 spokesperson added: “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.”
Jo Goodman, co-founder of Covid-19 Bereaved Families for Justice, said "Like thousands of others, I remember June 19 vividly. It was the day before what would have been my Dad’s 73rd birthday, shortly after he had passed away from Covid-19. It was a horrible time for my family, but we stuck to the rules, not even being able to hug to comfort each other.
"It’s completely sickening that the Prime Minister spent [it] sharing cake with 30 friends indoors and though we’re not even surprised any more, it still brings fresh pain. Whilst dozens sang happy birthday to him, families couldn't even sing in memory at their loved ones funerals.
"Regardless of any report, the Prime Minister clearly needs to resign. He’s lost all credibility."
The latest addition to partygate comes hours before Sue Gray was expected to release the findings of her investigation into Downing Street parties at the earliest.
Whitehall enforcer Ms Gray had just included Carrie Johnson into her inquiry amid claims of parties in the Downing Street flat she shares with the PM.
Over the weekend the Sunday Times revealed Mrs Johnson had invited two of her close friends a number of times to Number 11 Downing Street.
They were not working for Number 10 at the time despite Mrs Johnson's claims they were "work related".
It comes as the PM battles to save his premiership.
Just last week vocal Tory MP Christian Wakeford defected to the Labour party.
He sensationally walked across the Commons floor moments before PMQ's started last week to sit directly behind Keir Starmer and glare at the PM.
And more details have emerged of other Downing Street parties since the Mirror's initial reports last November.
Officials allegedly took part in a seven-hour drinking session at two separate dos to say farewell to Mr Johnson's top spin doctor and a Downing Street photographer in April 2020.
Photographs show the PM and his wife pictured sitting in the Downing Street garden with bottles of wine and a cheeseboard in May 2020.
Mr Johnson said those who attended were talking about work.
Five days after this gathering on 20 May 2020, around 100 people were invited via email to attend a "socially distanced BYOB drinks" party in the Number 10 garden.
Mr Johnson's Principal Private Secretary, Martin Reynolds sent the invites.
The PM and his wife were said to be with around 30 people who actually attended.
Mr Johnson said he was there for 25 minutes and thought it was a work event.