Boris Johnson has been sent a questionnaire by Scotland Yard over alleged parties in Downing Street, in a move that could raise fresh concerns among Tory MPs about his leadership. No 10 confirmed late on Friday night that the prime minister received the document, and vowed he would respond to it “as required”. About 50 people were asked to account for their presence at the dozen events under scrutiny by the police as part of their inquiry into Covid law breaches, named “Operation Hillman”. Johnson has continued to insist he broke no rules, but apologised for attending one gathering which was a “bring your own booze” garden party organised by his principal private secretary on 20 May 2020. He is also believed to have been present at a birthday celebration in No 10 on 19 June 2020 and leaving dos for aides in November that year, and January 2021. Police are also investigating a gathering in his personal flat in Downing Street. In a clear signal officers are investigating if the prime minister personally broke the law, a No 10 spokesperson said: “We can confirm the prime minister has received a questionnaire from the Metropolitan police. He will respond as required.” The move has the potential to spark fresh concerns among Tory MPs about Johnson’s future, though with parliament in recess, many will spend the next nine days back in their constituencies. Some backbenchers have held off calling for a ballot on his leadership until the outcome of the Met’s investigation, though suggested that they could submit a letter of no confidence if Johnson is found to have misled parliament or is fined for breaking the Covid rules he set. The Met declined to confirm the news that the prime minister had received the questionnaire nor whether those receiving them were being treated as potential suspects or witnesses. Earlier this week, Scotland Yard explained its approach and the role the questionnaire would play. It said the document “asks for an account and explanation of the recipient’s participation in an event” and “has formal legal status and must be answered truthfully”. The Met added: “Recipients are informed that responses are required within seven days. In most cases contact is being made via email. “It should be noted that being contacted does not mean a fixed penalty notice will necessarily be issued to that person. “Nevertheless, if following an investigation, officers believe it is appropriate because the Covid regulations have been breached without a reasonable excuse, a fixed penalty notice will normally be issued.” If police decide laws have been broken, then they will send the paperwork to the criminal records office, who will formally issue the fixed penalty notice. Cressida Dick, hours before she was forced out as the Met commissioner, said of those sent questionnaires: “Some, but probably not all, may very well end up with a fixed-penalty notice.” She added the scandal had “hugely disgusted many members of the public to see”.