Simon Case, the cabinet secretary, is among the senior civil servants facing disciplinary proceedings over the Partygate scandal, he has revealed, as he described some lockdown behaviour in Downing Street as “horrifying”. Appearing before MPs on the public administration and constitutional affairs committee, Case denied knowing about the alcohol-fuelled culture uncovered in the Sue Gray report. “These things weren’t ever brought to my attention,” he said. But asked if his own performance was being investigated, he said: “Yes of course, nobody should be excluded from the disciplinary process.” On the report, he said: “Mistakes were made, boundaries weren’t observed, some of the conduct described in Sue Gray’s report would be horrifying in any situation.” He said the independent civil service commission was overseeing the process, and that he was likely to reveal when it had been completed. “I certainly think it would be in the public interest for me to spell it out.” Some civil servants felt frustrated that Case escaped a fixed-penalty notice, and had not publicly taken responsibility for behaviour on his watch. He robustly defended his own role, however. In testy exchanges with the former shadow chancellor John McDonnell, he repeatedly said: “I take my responsibilities very seriously.” Asked about the failures of leadership, he added: “A number of people have left their posts.” McDonnell was pressing Case about why he had not launched an investigation into claims the prime minister sought a highly paid job for his then-girlfriend Carrie Symonds when he was foreign secretary. Case conceded he was unable to launch any kind of inquiry without the green light from Johnson. “I do not have an independent right of investigation,” he said. In what appeared to be an acknowledgment of Johnson’s tendency to push against convention, Case added: “The government of the day is one which is not remotely afraid of controversial policies. It believes it has a mandate to test established boundaries. It takes a robust view of the national interest … and it focuses very much on accountability to people in parliament, not on the sort of unelected advisory structures.” Tuesday’s hearing came after the chair of the committee on standards in public life urged Johnson to appoint a new ethics adviser immediately, or risk undermining public confidence in the rules. Christopher Geidt resigned as the prime minister’s ethics adviser earlier this month, saying he had been put in an “impossible and odious” position by being asked to rubber stamp a plan to maintain steel tariffs. Lord Geidt had previously conceded at a hearing with MPs that it was “reasonable” to ask whether Johnson may have broken the ministerial code by being fined for breaching Covid rules. After Geidt’s resignation, Downing Street made clear it would not immediately replace him and was instead reviewing the system for overseeing the ministerial code. In a letter to Labour’s deputy leader, Angela Rayner, Jonathan Evans, whose remit is to oversee standards in public life, said he believed that was unsatisfactory. “It is imperative that an independent adviser on ministers’ interests is appointed, even if temporarily, whilst proposals for the role are developed,” he said. Lord Evans pointed to a blogpost his committee published on 16 June, which made the point even before Geidt’s resignation that the regime for enforcing the ministerial code needed strengthening. “At a time of heightened concern about standards in public life, any change to the oversight of ministerial behaviour must be stronger, not weaker, than we have now,” it said. Evans pointedly copied his letter to Rayner to a string of senior government figures, including the prime minister, the levelling up secretary, Michael Gove, and the paymaster general, Michael Ellis, who often gets sent out to answer questions in parliament about Johnson’s probity. Rayner had written to Evans after reports that the prime minister tried to secure jobs for his now wife, Carrie Johnson, at the Foreign Office when he was foreign secretary, and later for an environmental charity.