Richard Moore’s decision comes after a list containing The Garrick club’s all-male and largely white membership was made public for the first time in a report by The Guardian newspaper earlier this week.
The club, founded in 1831 as a meeting place for gentlemen and named in honour of the 18th-century actor David Garrick, includes as members King Charles III, former prime minister Boris Johnson, various judges, parliamentarians, actors, and rock stars.
Moore sent a message to MI6 employees on Tuesday, acknowledging the reputational hit that news of his membership posed to the service – in particular the risk of it undermining its work to attract more women to join MI6.
He sent a second note to staff on Wednesday, saying that he had decided to quit the club, following conversations with senior female colleagues.
The club, whose members include actors Brian Cox and Matthew Macfadyen who starred in the award winning television show “Succession”, Benedict Cumberbatch, and Hugh Laurie, has around 1,500 mostly elderly members.
A large number of its members occupy influential roles – from government leaders to partners at top law firms and heads of consultancies, The Guardian said.
Moore’s resignation was followed by that of the prime minister’s most senior policy adviser, the civil service leader Simon Case, who quit the club on Wednesday afternoon.
Case had previously defended his membership of the club, telling MPs that it was “easier” to reform the all-male organisation “from within rather than chuck rocks from the outside”.
Hannah White, director of the Institute for Government think tank, which works with MPs and senior civil servants to make government more effective, said Case and Moore’s memberships sent a “terrible message” to junior civil servants.
Harriet Harman, the Labour MP who drafted the Equality Act 2010, said that clubs like The Garrick “prop up” structures that restrict women’s access to power.
Just over half of the club’s members supported a rule change to allow female members when the club last voted on the issue in 2015, but the motion failed because a two-thirds majority was required.
Another vote on the subject is expected in June.