Mr Bush thought the idea was hilarious and always tried to heckle back, according to Mary Matalin, a key adviser. But the Republican hierarchy became nervous at the media ridicule and Bob Teeter, Mr Bush's chief strategist, ordered Ms Matalin to "tell the President to stop talking to the chicken".

Eventually, the "fowl" stalked him at so many events that, in Mississippi, rally organisers persuaded the police to arrest him for disorderly behaviour.

Despite extensive efforts by both Bill and Hillary Clinton to distance themselves from Mr Livingstone, it emerges that he had been used extensively on the campaign. Another of his pranks was to infiltrate audiences with men in Pinocchio noses to cry out that Mr Bush had lied in a pledge not to raise taxes.

The trick may now be backfiring. Congressman William Clinger, chairman of the House panel investigating why the administration had 900 FBI files on its opponents, is using it to cast new doubt on Mr Clinton's assertion that the collection was an innocent "bureaucratic snafu".

Mr Clinger said yesterday he would ask the White House to explain how a "dirty tricks" operative such as Mr Livingstone came to be appointed to the "highly sensitive" post as chief of White House security.

The implication is that Mr Livingstone, who has resigned, was given the office, where he kept the FBI documents in a vault, as a cover for him to continue his stealthy work in providing the Clintons with ammunition against opponents.

Mrs Clinton has emphatically denied a report by a former FBI man who worked at the White House that she hand-picked Mr Livingstone for the post as part of her purge of staff she believed were disloyal.

After much evasion, the White House said on Sunday that Vince Foster, an old friend and legal colleague of Mrs Clinton, employed him. Mr Foster has been dead for three years.

1 July 1996: FBI agent tells of Clinton's 'secret trips to meet woman in hotel'

1 July 1996: FBI author 'tool in Right's plot to smear Clinton'