The foreign affairs committee last night accused BBC reporter Andrew Gilligan of changing his story.

Describing the journalist as an "unsatisfactory witness", the committee said parliament should be given new powers to compel individuals to name their sources.

During a private hearing, MPs are said to have broken into uproar when Gilligan appeared to suggest that his unnamed source may not have accused Alastair Campbell of inserting the 45-minute weapons claim.

Committee chairman Donald Anderson said the case against the government's communications chief had become "less strong" during the grilling.

Breaking News: Dr David Kelly, the source named as the possible MoD mole, has been reported missing by his family. Dr Kelly went for a walk yesterday afternoon and did not return. Local police said they are "concerned for his welfare".