Two courts have ruled that ministers will have to reveal details of every phone call, internal meeting and official engagement.
In a significant victory for transparency campaigners, two courts condemned the "secretive" culture of Whitehall and that government departments cannot rely on exemptions in the Freedom of Information Act to hide details of ministerial diaries from public scrutiny.
A report in the Independent, said that the rulings were embarrassing for the government because the High Court concluded that evidence by the Prime Minister's adviser on ministerial standards was "way below" what the public were "entitled to expect" of a senior civil servant.
Mr Justice Charles said the testimony of Sir Alex Allan, a former chairman of the Joint Intelligence Committee, had "lacked objectivity" and should be "roundly rejected".
He also accused Sir Alex of demonstrating a "determination to avoid directly conceding the indefensibility of things he had said" and a "keenness to repeat generalised lines... rather than give direct answers to questions".