Downing Street refused to allow a government minister to appear on the Question Time programme unless Tony Blair's former adviser Alastair Campbell was removed from the panel, the BBC has said.
No 10 said it questioned why Mr Campbell, rather than an opposition frontbencher, was representing Labour on the weekly programme.
The programme's editor said the request to replace Mr Campbell with a shadow minister was refused as a point of "fundamental principle".
Question Time host David Dimbleby explained the BBC's decision at the start of the show.
Watch the full debate at the