Tony Blair's top aide has been reported as saying that Gordon Brown will never become prime minister.

Boris Johnson, the Conservative MP and editor of the Spectator, claimed that Number 10 chief of staff Jonathan Powell told him it was a "Shakespearean tragedy" that the chancellor would never get the top job.

The alleged remarks have been strongly denied by Powell.

The prime minister's spokesman said: "There was some light-hearted banter... but the last person Jonathan would confide his innermost thoughts to is Boris."