Sir Ken Jackson, general secretary of the engineering union Amicus, has tipped Gordon Brown to succeed Tony Blair as prime minister.

Jackson, a close ally of the prime minister, said: "I don't think there is any doubt in the medium term if that position becomes available that Gordon Brown will fill it."

Jackson also criticised the Labour Party's new think-tank, Forethought. He said: "We need a new think-tank like we need a war."