JOHN Redwood's former special adviser has claimed that the Shadow President of the Board of Trade believed William Hague was the worst choice of the six candidates on offer to lead the party.

Mr Hywel Williams, Mr Redwood's special adviser at the Welsh Office, and leadership campaign manager in 1995 and 1997, is the latest author to try to embarrass the party leadership by exploiting the gulfs between the senior figures.

In a damning indictment of Mr Hague, Mr Williams writes in a book called Guilty Men that Mr Redwood believed all the candidates had qualities but wrote of Mr Hague's bid as ''one of unredeemable train-spotting vacuity overlaid by the gloss of management theory''.

Last night, senior Tory sources would not comment on the claims and implied Mr Williams might be an embittered former colleague who wanted to hog the headlines before his book was published later this month. A senior Conservative spokes-man said: ''We don't intend to dignify the rubbish in this book with a comment.''

Labour last night challenged Mr Hague to sack Mr Redwood from his Shadow Cabinet.

The author also takes a swipe at Mr Redwood's campaign manager, Iain Duncan Smith, who he claimed used the campaign only to further his ambitions.

Mr Williams claimed Mr Duncan Smith had proved to be a ''difficult corporal'' who amended Mr Redwood's written statements ''in a way that the candidate's mercurial spirit found lumbering, conceited, and mentally third rate''.

Mr Williams has even claimed Mr Redwood's followers had made ''cruel insinuations'' about the bachelor nature of Mr Hague's circle. He said Mr Duncan Smith was crass in talking about ''the bachelor boys'' running the campaign.

The Times, which is serialising the book, said that Mr Redwood had had virtually no contact with Mr Williams in the past year and had not been consulted about the book or seen advance copies.

Trade Minister Barbara Roche said last night: ''John Redwood's complete contempt for William Hague is now out in the open.

''The barely-concealed hatred between the two men has now been revealed by one of Mr Redwood's closest aides.

''The Tories are as split as ever and now we know Mr Redwood is simply waiting for a new opportunity to run for the Tory leadership.

''Mr Hague should act now and remove a Shadow Cabinet member who so clearly opposes his leadership.''