Veteran broadcaster Sir David Attenborough has confirmed that he was asked by the BBC to sign a letter to the Prime Minister calling on him to protect the corporation from cuts.
Sir David - a former controller of BBC2 - said it was "perfectly proper" for the BBC to arrange an open letter in this way to ensure that its supporters' voice was heard. Reports have suggested that the letter may have been orchestrated by BBC director of television Danny Cohen.
The letter came ahead of the publication of a green paper launching the 10-yearly review of the BBC's Royal Charter, which will consider the future of the licence fee and look at whether the broadcaster should continue to provide the range of services currently on offer.
Culture Secretary John Whittingdale sparked speculation that the BBC may be told to cut back on popular programming which competes with shows available on commercial broadcasters or to reduce its online presence, when he questioned whether the corporation should try to be "all things to all people".
And he raised questions about the future of the licence fee, suggesting that the BBC could switch to a subscription service in the long run.
Sir David was joined by James Bond actor Daniel Craig, Oscar-winner Dame Judi Dench, author JK Rowling, comedian Miranda Hart and presenter Chris Evans, in calling on David Cameron to ensure the Government does not turn the BBC into "a narrowly focused market-failure broadcaster".
Describing the BBC as "the envy of the world," they warned: "A diminished BBC would simply mean a diminished Britain.
"Like all organisations, it has its faults but it is overwhelmingly a creative force for good."
Asked on Radio 4's Today programme whether the BBC had asked him to sign the letter, Sir David said: "Yes."
He added: "The BBC has to defend itself, and quite properly. Like any institution if you want to have your supporters' voice heard, you go about helping that to happen. That's a perfectly proper thing to happen.
"It's like all these things. You get a letter written by various people. I don't know who it was written by. I was sent a copy of it and it seemed to me to be common sense and I very gladly put my name to it."
Sir David said it was right for the BBC's remit and functions to be regularly reconsidered in the charter review process.
"The broadcasting landscape is changing and changing radically and broadcasting organisations have to change in order to deal with that properly, so it's quite right and proper that the function of the BBC in detail should change as the landscape changes," he said.
"Its fundamental function of providing public service broadcasting hasn't changed."
Asked whether his own record of producing natural history documentary for organisations other than the BBC was proof that commercial producers and broadcasters were capable of delivering high-quality programming, Sir David said: "By government edict, by government law, the BBC has to take a certain proportion of its programmes which are made by independent broadcasters, independent production companies, and I worked for those and although they were made by independent production companies, they have been shown on the BBC.
"I've also made some 3D programmes and they haven't been shown on the BBC because the BBC doesn't have a 3D network so they couldn't be shown there."