Four more Conservative MPs called for Boris Johnson to resign on Thursday over lockdown-breaking parties, as Downing Street sought to contain the political aftermath of the Sue Gray report. The prime minister’s allies reiterated the defence that his attendance at a series of gatherings for departing staff was permitted as work duties. His official spokesman argued that Covid guidelines did not specifically rule out leaving drinks. He also formally apologised for misleading the media in repeatedly denying that any parties had taken place inside Downing Street during lockdown. He insisted this had been entirely inadvertent. Nineteen Tory MPs have publicly called for Johnson to quit so far, well below the 54 required to prompt a confidence vote, but the trickle of new voices will unnerve Downing Street as backbenchers digest Gray’s description of rowdy and drunken gatherings inside No 10. Along with those who have made public calls, two more have submitted and then withdrawn letters of no confidence, and at least three others have called for Johnson to resign but said they would not submit letters. The former health minister Stephen Hammond was among those to say he had submitted a letter of no confidence. Hammond, who has a majority of 628 in his Wimbledon seat, described the conclusions of the Gray report as damning. “I cannot and will not defend the indefensible,” he said. “I am struck by a number of my colleagues who were really concerned that it’s almost impossible for the PM to say I want to move on, as we cannot move on without regaining public trust and I am not sure that’s possible in the current situation.” Two other MPs, David Simmonds and John Baron, said they had lost confidence in Johnson. A fourth, Angela Richardson, who quit as a parliamentary private secretary earlier in the year, said she would have resigned if she had been in Johnson’s position. Baron, a former shadow minister, said he did not believe Johnson was unaware of the “shameful pattern of misbehaviour during the pandemic as the rest of us kept to the Covid regulations”. Simmonds, the MP for Ruislip, Northwood and Pinner, which adjoins the prime minister’s Uxbridge and South Ruislip constituency in west London, said it had become clear that “while the government and our policies enjoy the confidence of the public, the prime minister does not”. Speaking about Gray’s findings, Richardson said: “I am clear that had this been a report about my leadership, I would resign.” Julian Sturdy, the MP for York Outer, had called on Johnson to go on Wednesday. The report had left him “unable to give the prime minister the benefit of the doubt,” he said. MPs said on Thursday that they expected the number of letters to increase to continue over the next few days, but stressed it was not a coordinated effort. Others have hinted at deep dissatisfaction in emails to constituents seen by the Guardian. Andrew Jones, the MP for Harrogate and Knaresborough, wrote that he was “in no way sympathetic to fancy words or formulae that allow anyone to pretend they were at a work event when they clearly were not”. Rob Largan, the MP for High Peak, said he was “taking the appropriate action to defend integrity in public life.” Philip Dunne, the MP for Ludlow, wrote to a constituent that he had grave doubts about the PM. “I am sorry to say any benefit of the doubt the PM enjoyed has now been eroded,” he wrote. “While I have not called for his resignation, the PM has yet to prove to me that he is the right person to ensure the return of integrity and due decorum, that all our constituents expect from politicians.” When Johnson’s spokesman, a civil servant who by convention is not named when quoted, apologised for misleading the media, he refused to say whether he had attended any of the events set out in Gray’s report or whether he had received a fixed-penalty notice. “The prime minister has said, and I’ve said on a number of occasions that there were failings both in terms of what happened and in terms of how it was handled subsequently,” he said. “The prime minister has apologised for that, and I’m happy to apologise for that as well.” He said Johnson had been entitled to attend a series of leaving drinks, including one where he has pictured, glass in hand, raising a toast, as the “guidelines were silent” on whether such events were permitted. Steve Barclay, the minister brought n as Downing Street chief of staff as part of the Partygate shake-up at No 10, argued the prime minister saw such events as permissible because staff were working “closely together for long hours”. The publication of Gray’s report has reignited scrutiny of the parallel Metropolitan police investigation into the gatherings in and around No 10, and notably the question of why Johnson was fined for only one other event – his own birthday party in June 2020 – when he had attended other gatherings for which staff were penalised. The Met’s acting commissioner vehemently rejected the notion that Johnson had received favourable treatment, saying the force had investigated the parties “without fear or favour”. Giving evidence to the London assembly’s police and crime committee on Thursday, Stephen House said fixed-penalty notices were only issued if police “had the evidence that we thought would give us a realistic prospect of a convention at court” should the fine be challenged. “Without making comment on any individual, I don’t believe there is clear evidence that the prime minister breached many other times,” he said. “I am very confident of the integrity of the decisions that were made in this investigation. I’m not particularly concerned about what the prime minister thinks. I do my job without fear or favour, as did the Met.” House said he accepted some photographs of No 10 gatherings “look bad”, but added: “We deal with the law, not what looks bad. And just because there is alcohol present, can I remind people that the Covid regulations are about breaching Covid regulations. They are not about whether there is drink there or not.” He also rejected the idea that Johnson or other senior No 10 staff might have avoided sanction by not filling in police questionnaires about their activities. He said someone doing so would be “a spur for more work, not less”, and that the “vast, vast majority” of questionnaires were returned.