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 on May 20, 2020 during lockdown, his former aide Dominic Cummings has said.  Cummings made the claim on social media on Monday evening. He has repeatedly attacked his former boss since resigning as Johnson's former chief adviser in November 2020. 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. Deputy PM Dominic Raab denied the allegation.