Government-owned broadband builder NBN Co claims the reputations of its directors could be damaged if it revealed which of them turned up to a September board meeting.

Freedom-of-information expert Peter Timmins said NBN Co's claim was ''speculative, ridiculous and without foundation'' and there were signs a culture of secrecy was spreading through Canberra.

Fairfax Media requested the minutes of the September 20 meeting to discover how the directors reacted to being asked to resign by Malcolm Turnbul. Credit:Rob Homer

NBN Co FOI officer David Mesman made the claim in a decision denying Fairfax Media access to minutes of the meeting.

''If NBN Co were to publish a director's attendance, it could also damage a given director's personal reputation and ability to sit on other boards,'' Mr Mesman said.