The head of the civil service, Simon Case, and the MI6 chief, Richard Moore, have resigned their memberships of the Garrick Club after intense criticism of their decision to join a club that has repeatedly blocked the admission of women as members. Their resignations come two days after the Guardian published for the first time details of the club’s closely guarded membership list, revealing that fellow members include judges, scores of senior lawyers, leaders of publicly funded arts institutions and King Charles. The moves by Case and Moore are likely to put pressure on other high-profile members of the club to rethink their membership. Case, who as cabinet secretary is the leader of half a million civil servants, had faced condemnation for arguing he only joined the London gentleman’s club in an attempt to overturn its all-male policy. The Cabinet Office confirmed on Wednesday afternoon that Case had resigned his membership. It is understood that Moore, chief of the UK’s Secret Intelligence Service, decided to quit the Garrick after criticism from colleagues at MI6, which has repeatedly restated its commitment to improving the service’s poor record on equality and diversity. Moore is understood to have written to all MI6 staff twice within the space of 24 hours. The first message, sent to thousands of its employees on Tuesday morning, addressed the Guardian’s coverage and acknowledged the reputational hit that news of his membership posed to the service, and in particular the risk of it undermining its work to attract more women to join MI6. In that note, he said he would not be resigning because he was campaigning from within the club for women to be allowed to join. But at 9am on Wednesday he sent a shorter note to staff saying that on further reflection overnight he had decided to quit the Garrick, the Guardian understands. He is also understood to feel mortified at the attention surrounding his club membership because it has detracted from MI6’s work to address the under-representation of women. The resignation followed conversations with senior female colleagues. On Tuesday Case had been asked by the former Labour minister Liam Byrne how he could “foster a genuine culture of inclusiveness” while also being a Garrick member. He replied: “I have to say today my position on this one is clear, which is that if you believe profoundly in reform of an institution, by and large it’s easier to do if you join it to make the change from within rather than chuck rocks from the outside.” Hannah White, director of the Institute for Government thinktank, which works with MPs and senior civil servants to make government more effective, said Case’s justification of his membership was “bizarre”. She said Case and Moore’s membership sent a “terrible message” to junior civil servants. “The signals senior leaders send are tremendously important. I can just imagine layers of women within the civil service and MI6 looking at these names and wondering: ‘what are the conversations that are going on there, which I can never be party to?’” News of Moore’s membership of a club that has refused to admit women since it was founded in 1831 came after a concerted drive by MI6 to demonstrate that it is no longer staffed exclusively by white, male Oxbridge graduates and is open to a wide range of applicants. On its website, the service says it “is committed to building a workforce that reflects the society we serve”. Tweeting from the @chiefMI6 account, Moore has previously expressed his service’s commitment to diversity, attempting to shake off the popular perception of what a typical British member of the secret services should look like, with the hashtag #ForgetJamesBond. Sir Robert Chote, a prominent economist who chairs the UK Statistics Authority, also resigned from the club on Tuesday morning, according to the Financial Times. Chote, a former director of the Institute for Fiscal Studies, was said to be anxious to avoid causing controversy for UKSA. As revealed by the Guardian this week, the Garrick’s membership includes a supreme court judge, five court of appeal judges, eight high court judges, about 150 KCs, dozens of members of the House of Lords and 10 MPs, plus heads of influential thinktanks, law firms, private equity companies, academics, prominent actors, rock stars and senior journalists. The publication of the names of judges who are members has triggered unease from female barristers. Helen Mountfield KC, a specialist in equality law, said: “I would not feel that a client of mine was getting a fair hearing in a case concerning sex discrimination which was heard by a judge who was a member of the Garrick Club.” She added: “Deciding to be a member of a club, open to members on the basis of professional attainment, and in which informal connections are made, seems to suggest that a person is prepared to tolerate discrimination and bias.” Karon Monaghan KC, a senior barrister, said she had long felt uncomfortable when she had to appear in front of judges who were rumoured to be members of the Garrick. While she was not calling for judges to resign from the club, she said transparency about membership was important and warned that there were some cases where it would be inappropriate for a Garrick member to appear as judge. “Garrick members should consider recusing themselves if they are hearing a sex discrimination case, rape case or a case involving sexual violence. In a rape case, you’re having to direct a jury in relation to things like sex stereotyping and how you should approach the evidence of a victim. Do we want a male judge who thinks it’s appropriate to exclude his female peers from a club to be making judgments on sex stereotyping? “In a sex discrimination case you might be arguing that a woman has been excluded from certain benefits or opportunities within a professional context, in front of a judge who is a member of a club, along with his judicial peers, in which female members of his profession are excluded. It’s completely unacceptable; in these cases it should be argued that a judge who’s a member of the Garrick club should recuse himself.” The US federal code of conduct for judges states that they “should not hold membership in any organisation that practises invidious discrimination on the basis of race, sex, religion, or national origin”, adding that such membership “gives rise to perceptions that the judge’s partiality is impaired”.