The future of the BBC should be decided by the public, rather than politicians with vested interests, the chairman of the broadcaster's governing body has said.
BBC Trust boss Rona Fairhead said MPs should not be allowed to unduly interfere with the editorial decision-making by the public service institution.
Her comments come as the Culture, Media and Sport Committee prepares to scrutinise the BBC's charter review, which sets the parameters within which the corporation operates.
Culture Secretary John Whittingdale previously said the review would look at whether the BBC should continue to be "all things to all people" or have a more "precisely targeted" mission.
Writing in the Independent, Fairhead said the power balance should instead lie in the hands of the public.
She said: "We need to be clear about the BBC's future priorities and exactly what changes need to be made.
"But this should all happen through a proper debate in which the public's voice is heard loud and clear. The BBC's future is simply too important to be settled behind closed doors."
She added: "There remains the question of whether the BBC should be a universal service. Some argue that it should address only areas in which the market fails, with a schedule of news, current affairs, children's programmes, science, art and religion.
"We recognise that the BBC can't be all things to all people, but we fundamentally support a BBC that everyone pays for and from which everyone benefits.
"Across many fronts it is clear that demands on the BBC budget will only increase.
"Where sport is concerned, there may be a case for new regulation to protect certain crown-jewel events that bring the nations together when broadcast on free-to-air networks."
Fairhead said the BBC would not be able to afford making blockbuster shows such as Game Of Thrones or House Of Cards.
She said: "Despite examples of the US system producing some extraordinarily high-quality output, it does so at a cost that is way beyond the BBC's capacity to pay."
The BBC Trust previously said MPs should be given a vote on any future plans to change BBC funding.
The trust's response to the Government's recent green paper on the future of BBC said the current 10-year charter could be extended by another year and argued for "a legal obligation" in the next charter to make sure there was "parliamentary approval for any change to the BBC's funding".
The trust, which has also published a series of questions asking audiences for their views on the BBC, said the broadcaster was built on "a broad mission" including news coverage and entertainment.