London (CNN)British Prime Minister Boris Johnson celebrated his birthday with a gathering at his official residence in June 2020 while the United Kingdom was in its first Covid-19 lockdown, a spokesperson said Monday, marking the latest scandal for the country's leader.
In a statement, a Downing Street spokesperson 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."
Under Covid-19 restrictions at the time, indoor gatherings were not allowed, with people permitted only to meet outside in groups of up to six people.
CNN affiliate ITN reported Monday there were two gatherings held to celebrate Johnson's birthday: one attended by as many as 30 people held at the cabinet office the afternoon of June 19, and another that evening that was hosted at Johnson's residence and attended by family friends.
According to ITV News, Johnson's wife, Carrie, organized the small gathering in the Cabinet Room. A source who worked in Downing Street at the time has independently confirmed to CNN that the gathering took place on that day and that it was arranged by Carrie, who led the singing of the happy birthday song.
CNN understands that the gathering was largely attended by what was deemed to be Johnson's inner circle at the time.
Downing Street has denied that any rules were breached by the evening gathering, with a spokesperson saying: "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."
Johnson has been under pressure for weeks over alleged summer garden parties and Christmas gatherings held in Downing Street when the rest of the country was under strict Covid restrictions.
A report into the allegations, set to be released this week, could be the final straw for Johnson's increasingly mutinous party.
Johnson's approval ratings are plunging and there appears to be a growing sense among some parts of his ruling Conservative Party that he is becoming a liability. Two polls in the past week suggested that as many as two-thirds of voters want him to resign.
The Prime Minister has given unconvincing answers when asked about the numerous parties. First he said there were none. Once undeniable evidence emerged, he denied knowing about the gatherings. When a photo of him at one such event was published, he insisted he didn't realize the gathering was a party, saying he "believed implicitly that this was a work event."
Johnson was even forced to apologize to the Queen after it emerged that a party was held in Downing Street the night before the funeral of Prince Philip. It was noted at the time that because of Covid-19 restrictions, the Queen was forced to mourn her husband at St. George's Chapel at Windsor Castle while sitting alone.
CNN's Ivana Kottasova contributed to this report.