David Blunkett has told Gordon Brown that he should not take succession to the Labour leadership for granted.

The home secretary, who has clashed with the chancellor over the comprehensive spending review, called for unity in the run-up to the general election.

"It is important that those of us who are privileged, at the very cutting edge of government, at the centre of events, don’t presume that we should be immediately taking somebody else’s job," he said.

"I think Tony’s never been more vital in his approach. His vitality has been evident to all of us. His determination to create, through the strategic plans and the manifesto, a radical reforming third term is undeniable, and all of us know that we sink or swim together."

When asked how much of a third term Blair should serve, he said: "I’d like the prime minister to remain as long as he feels he has the drive, the energy and leadership to do it, and I see no sign of those diminishing at all."