British Prime Minister Boris Johnson lied to parliament when he claimed he did not know of his staff’s plans to hold a drinks party during lockdown, his former aide Dominic Cummings has said. Johnson is already battling damaging “Partygate” allegations that he and staff attended boozy events during lockdowns and a senior civil servant is investigating the claims.

The prime minister has apologized for a May 20, 2020, party in the garden of Downing Street, but said he did not know about it in advance and thought he was attending a work event. Cummings, who himself has been accused of breaking lockdown rules in spring 2020, made the claim on social media on Monday evening. He has repeatedly attacked his former boss since resigning in November 2020.

Johnson’s former chief adviser wrote that the party was arranged by the prime minister’s principal private secretary, who was told by two senior officials to cancel it and would have checked this with Johnson. Cummings said he himself warned the prime minister over the party, saying Downing Street was becoming a “madhouse”, but Johnson “waved it aside”.

“The events of 20 May alone, never mind the string of other events, mean the PM lied to Parliament about parties,” said Cummings.

“The suggestion that the PM was warned (about the party) is not true,” deputy Prime Minister Dominic Raab insisted to BBC Radio 4, after a presenter said Cummings “threw a grenade in the direction of his former boss”.

Raab told Sky News that “the prime minister has been very clear that’s not true, accurate”.

Johnson is facing calls to stand down from several senior MPs over allegations of illegal parties, during national lockdown measures.

Downing Street has apologised to Queen Elizabeth II after it emerged that his staff held leaving parties during a period of national mourning for her husband, Prince Philip, in April 2021.

The Times wrote Tuesday that Johnson has “sustained immense damage” from the revelations.

Cummings said in his blog that a May 15, 2020 gathering in the Downing Street garden that he himself is pictured attending along with Johnson and his now-wife Carrie, was not a party, however. He said staff were encouraged to hold meetings outside at the time and while there was wine at the table, they were discussing work issues.