The BBC's Chairman Sir Michael Lyons says that the BBC "cannot continue to grow forever".
Interviewed by Today presenter John Humphrys, Sir Michael added that the corporation's proposed new strategy, outlined yesterday by its director general Mark Thompson, is "attractive".
He said that the BBC "needs to send message out that the BBC is not on some onward march, there are boundaries to what it can and should do". But he denied that the corporation was merely seeking popular hits. "I don't think we're actually swayed by ratings," he said.
The new strategy, titled Putting Quality First, earmarks digital radio stations 6 Music and Asian Network for closure, and would scale back the BBC website.