Bob Woodward, the Washington Post reporter who broke the Watergate story that brought down President Richard Nixon, testified before the special prosecutor investigating the outing of a covert Central Intelligence Agency operative.

In the latest twist in an investigation that has brought indictments against Lewis “Scooter” Libby, the former chief of staff to Vice-President Dick Cheney, Mr Woodward testified that he was given the name of the agent, Valerie Plame, a month before she was publicly identified by columnist Robert Novak.