The U.K. election campaign, focused for months on topics like the economy and bankers' bonuses, veered Sunday to a more personal issue for Prime Minister Gordon Brown: his temper.

Mr. Brown was accused, in separate accounts, of temper fits and the bullying of staff members. The accusations—one in an excerpt from a new book, the other from a charity hot line that receives complaints about bullying behavior—unleashed a debate about the character of a leader who has a reputation in political circles for bad-tempered outbursts and moody self-reflection.

Mr. Brown and several political allies rejected the accusations.

The Observer newspaper carried material from a book on Mr. Brown by its political commentator, Andrew Rawnsley, that alleged the prime minister has acted aggressively with staff, including grabbing them by the lapels of jackets, shoving them aside and shouting at them. The book alleges that Sir Gus O'Donnell, the head of the civil service, was so concerned that he launched an investigation into incidents and talked to Mr. Brown about his attitude toward staff.

A spokeswoman for Sir Gus said it is "categorically not the case" that he ordered a probe or warned Mr. Brown about his behavior. A spokesman for Downing Street said: "These malicious allegations are totally without foundation."

A host of senior politicians took to the airwaves to deny that Mr. Brown was a bully, with Peter Mandelson, the influential business secretary, saying Mr. Brown "gets angry but chiefly with himself" and is a man "who doesn't bully people." Home Secretary Alan Johnson said Mr. Rawnsley had a book to sell.

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