TORY leader Iain Duncan Smith vowed last night to fight to keep his job after rebel Conservative MPs triggered a confidence vote.

He will make an impassioned appeal to backbenchers this afternoon at a meeting of the party's 1922 Committee, only minutes before the secret ballot begins.

The result of the ballot will be announced by the chairman of the committee, Sir Michael Spicer, at about 7pm.

Mr Duncan Smith needs a simple majority to win. Defeat would trigger a lengthy leadership contest.

Victory would rule out any new challenge for 12 months under rules introduced by predecessor William Hague to shore up his leadership.

But if he fails, Mr Duncan Smith will be barred from standing in the ensuing battle for the Conservative crown.

The field is then open to leadership hopefuls whose names have been the subject of mounting speculation at Westminster for weeks.

Mr Duncan Smith began his survival struggle on the steps of Conservative Central Office yesterday afternoon, after being informed by Sir Michael that the 25 letters needed to trigger a vote had arrived.

He appealed for the party not to plunge itself into a fractious leadership election that could last months and urged colleagues to give him a renewed mandate.

Mr Duncan Smith said: "Yesterday, I called on the parliamentary party to end this ludicrous leadership speculation that has been going on for the past few weeks. I said to end it by Wednesday.

"I can therefore say today that I welcome and am pleased that we will have an opportunity to do that.

"I will absolutely submit my name for a renewed mandate to lead the party to the General Election and to win.

"We should not now let the Government off the hook by giving them this opportunity, by plunging ourselves into a fractious leadership election that could last months and give the Government an opportunity to escape proper scrutiny.

"Therefore, I will address the '22 Committee, my colleagues, and urge them to renew that mandate for me to go forward, and to put an end once and for all to the speculation that has been sapping away at this party."

Former Tory leader Mr Hague vowed to support Mr Duncan Smith in today's vote - despite being in Japan on business.

The Richmond MP, who has offered staunch support to his successor throughout the leadership crisis, has arranged for another MP to submit his vote by proxy.

Anne McIntosh, MP for Vale of York and a transport spokeswoman, also pledged loyalty to the leader and attacked the plotters who have sparked the contest.

But David Curry, MP for Skipton and Ripon, said he was almost certain to vote against Mr Duncan Smith, insisting it was impossible for him to rebuild his authority.

Mr Curry was set to join Ryedale MP John Greenway in the "anti-IDS" camp.

Mr Greenway has admitted being among the 25 MPs who have demanded a confidence vote.

Last night, the Ryedale MP urged Conservative MPs to unite around a single potential leader to avoid the "bloodbath" predicted by Mr Duncan Smith.

Mr Greenway declined to say who should be the successor, but has previously identified Shadow Chancellor Michael Howard as the candidate with the best qualities.

He said: "I would like the party, in Parliament, to endorse one candidate as leader. We can then go to the party in the country to get their endorsement for that person and avoid the kind of bloodbath that Iain's talking about.

"It need not come to that."

But Ms McIntosh - a supporter of Kenneth Clarke in 2001 - said: "I don't believe there is any merit in changing the leader at this stage of the Parliament.

"It's regrettable that factions in the party have undermined Iain Duncan Smith. They undermined John Major and William Hague, and you wonder where it will end?"

Mr Curry - another Clarke backer two years ago - said: "It's difficult to see how Iain's authority can be re-established. With a General Election perhaps only 18 months away, we need to focus on that."