The prime minister is being questioned by Scotland Yard investigators over his role in up to six of the gatherings held in Downing Street while restrictions on mixing were still in place.
Mr Johnson, who has appointed his own lawyer, is set to claim the three leaving parties he attended were part of his job. “Saying goodbye to staff is part of working life,” a source told The Times.
Defence minister James Heappey said on Monday that the prime minister would argue that he is “not culpable” of the potential offences being probed by the police.
“I certainly don’t think the prime minister should volunteer his culpability,” the minister told Sky News. “His argument is that he is not culpable. We should wait and see what the police come back with.”
Asked about the photo showing Mr Johnson alongside several staff and bottle of bubbly at a Christmas quiz, Mr Heappey added: “That is a snapshot in time. I don’t know if the prime minister has walked into that room whilst the other two people in the photograph are engaged in something.”
Mr Johnson received the questionnaire from police investigating allegations of lockdown-breaching parties late on Friday evening, and is consulting with a lawyer on responses this week.
The PM has already claimed that he believed “implicitly” that the “bring your own booze” garden party at No 10 in May 2020 was a work event.
He will reportedly also claim that he was working in his own flat in 11 Downing Street on the November 2020 evening that Dominic Cummings claims a party was held.
Former Conservative leader Sir Iain Duncan Smith has said it would be “very tough” for Mr Johnson to survive if the police probe concludes that he broke Covid laws and gets a fixed penalty notice.
Senior Tory backbencher Sir Bob Neil also said a fine could be fatal. “I think it will be very difficult for anyone to be in the position of the country’s principal lawmaker, and then break a law which they themselves had brought into force,” he said.
But allies have said Mr Johnson, who faces a potential no-confidence vote if 54 Tory MPs send in letters, intends to carry on even if he is fined by the police.
Almost 90 questionnaires will be sent to staff working at Downing Street, according to The Times, more than the 50 originally announced by Scotland Yard.
Rishi Sunak said on Friday that he is not expecting to be asked to fill out a police questionnaire in relation to the Partygate probe. The chancellor said he did not think he had broken Covid rules when he went to a birthday event for Mr Johnson in June 2020.
Adam Wagner QC, a leading legal expert on Covid rules, has suggested it could take “months” for Scotland Yard to conclude its investigation if Mr Johnson is “lawyered up”.
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