Duncan Smith tells Tories to avoid back-biting as cracks appear in party unity

The Conservative Party will not regain power unless it stamps out the infighting that has dogged the party for almost a decade, contenders for the party leadership have been warned.

Iain Duncan Smith, the former party leader, spoke out in an interview with The Independent as the first cracks appeared in the show of unity that has surrounded the contest for the Tory crown, fuelling fears of a " disastrous" return to the back-biting of the past.

David Cameron and David Davis were forced to distance themselves yesterday from claims that the shadow Home Secretary may abandon frontline politics if he is demoted in a reshuffle following a Cameron victory.

Voting in the long-running Tory leadership election will end at noon today, and the result will be known tomorrow.

Mr Cameron was said to be "very angry" at reports suggesting that he would offer Mr Davis the lower-profile post of Defence Secretary, perhaps combined with a title of deputy party leader, if as widely expected, he is victorious in the ballot of party members.

One aide said: "He is very angry about these briefings given to the Sunday papers. He strongly disapproves of this sort of shoddy approach.

"He wants a shadow cabinet of all the talents and will be seeking people on the basis of their talents."

Allies of Mr Davis also drew back from claims that he might refuse to serve on the front bench if he is demoted from his prestigious role as shadow Home Secretary. But they insisted that he expected a senior position in any Cameron shadow cabinet.

One source said activists had made clear their desire for Mr Davis to play a major frontbench role during the private hustings over the past month. He said: "The party would expect him to have a very big role."

The row highlighted the dilemma facing Mr Cameron as he considers the crucial question of the make-up of his shadow cabinet. William Hague is tipped for a return to front line politics as shadow Foreign Secretary and the former leadership contender Liam Fox is also predicted to have a significant role. George Osborne, the shadow Chancellor and a close friend of Mr Cameron, is expected to keep his job.

Mr Cameron's biggest handicap could be the lack of discipline among Tory MPs, and their history of "backbiting" and briefing against the party leader, Mr Duncan Smith.

Mr Duncan Smith, who was ousted as leader in November 2003, said: "I want David Cameron not to have to put up with what William [Hague] and I put up with, when every time you want to say something you've got 10 MPs going off and rubbishing what you're saying, which happened to both of us.

"We can't do that any more, because if we do that, David Cameron is never going to succeed. He has to have discipline behind him so that even if we disagree, we must never turn it into an attack on the leader. He's got to develop, like Thatcher developed in '75 to '79.

"And when he makes a mistake, and he will make mistakes, and when he fails ­ and he will fail on certain things ­ the test for us is whether we can hold our nerve and say nothing."

Mr Hague, who was Conservative leader from 1997 to 2001, also issued a warning to Mr Cameron. Writing in the News of the World, he said: "Keep your friends close, but your enemies closer. This is a very old political saying, but it's very true in your shadow cabinet."

Some Tory backbenchers are worried that allies of Mr Davis may destabilise a Cameron leadership if he is rebuffed in the shadow cabinet reshuffle, while others fear a parliamentary takeover by members of the so-called Notting Hill set.

One Conservative MP said: "The talk in the tearoom is of great nervousness at what will happen under the new leader.

People say there would be no trouble if Davis was leader because they would stamp on it. The opposite is true of David Cameron."

A victory by Mr Cameron would, however, lever in support from a wealthy group of donors who have helped to support his leadership campaign. They include Lord Harris of Peckham, the carpet magnate, Simon Wolfson, chief executive of Next, and Susie Anstey, the wife of Lord Ashcroft.