Tory chairman Grant Shapps said the BBC must tackle a culture of secrecy and waste in the wake of the Jimmy Savile scandal, rows over stars' salaries and pay-offs to senior executives.
He said there was a "question of credibility" for the BBC over whether it applied "fairness" to its reporting of politics.
With the BBC's royal charter coming up for renewal in 2016, Mr Shapps said there were "lots of different ways" in which licence fee-payers' money could be used to fund public service broadcasting.
And he said the £145.50 annual fee would be too much if the BBC failed to reform.
"In order for the public to have confidence, the only way they can do that is to really go for a much more transparent, open deliberate policy," said the Tory chairman.
"If they do that they can make sure they win back public trust. If they don't, they are in danger of frittering away Auntie's public trust that has been built over a long time."
A BBC spokesman said: "Mr Shapps is right that transparency is key to the future of the BBC.
"We are proud of the quality of our news and its commitment to reporting without bias. Where we believe or are shown to have erred, we correct and apologise."