Revelations of birthday gatherings come in the week an official report on Downing Street parties during COVID-19 lockdowns is due to be published.

Britain’s Prime Minister Boris Johnson is under mounting pressure after his office admitted to another Downing Street gathering, this time to mark his birthday in 2020.

The birthday celebration took place on the afternoon of June 19 and was organised by Johnson’s wife who brought in a cake, ITV News reported.

There were about 30 people at the event, including Lulu Lytle, the interior designer who was leading a controversial renovation of Johnson’s flat and was not a member of staff, the broadcaster said. The party, which included the group singing Happy Birthday to Johnson, lasted for between 20 and 30 minutes.

“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,” Downing Street said in a statement in response to the report.

ITV and the Independent also reported that a group of family and friends also celebrated later that evening in Johnson’s flat.

“This is totally untrue,” the prime minister’s office said.

Johnson is already facing a slew of allegations of sometimes ‘boozy’ parties held during the 2020 and 2021 lockdowns in breach of the government’s own pandemic rules. An official investigation into the events, which have fuelled widespread public anger in a country with the highest number of COVID-19 deaths in Europe, is due to be published this week.

Does a cake make a party?

Does singing happy birthday qualify as a party?

The point for many people is… it was more of a party than millions had, including many who sadly wouldn’t see another birthday.

— Paul Brand (@PaulBrandITV) January 24, 2022

“Johnson has completely lost his authority,” Nick Timothy wrote in the rightwing Daily Telegraph. Timothy was Downing Street chief of staff in the government of Theresa May, Johnson’s Conservative predecessor.

“The collapse in Johnson’s authority is causing widespread political dysfunction and further danger for the Conservatives,” he said. “Johnson is no longer popular, he is no longer powerful.”

57-year-old Johnson’s government has been tarnished by a string of controversies, including Lytle’s costly renovation of his Downing Street apartment and persistent allegations of ministerial corruption under his watch.

Johnson is also facing new allegations of Islamophobia within his party after Nusrat Ghani, who lost her job as a junior transport minister in February 2020, told the Sunday Times that she had been told by a “whip” – an enforcer of parliamentary discipline – that her “Muslimness” had been raised as an issue in her sacking.

The Conservatives won a landslide victory in the 2019 elections, but the latest opinion polls show the opposition Labour Party now has more support.