He began his last-ditch effort to save his job by saying the public would wonder "what in hell's name" the Tories were doing if they plunged themselves into a leadership contest at a time when they should be taking on the "failing" Labour government.

Mr Duncan Smith insisted he was "going to fight" for the British people and said he could not walk away from the confidence vote because he was "not a quitter".

The secret ballot lasts from 1530 to 1830 GMT on Wednesday with a result expected about half an hour after voting ends.

If he fails to get a majority of the votes he would lose his job, and be ruled out of the ensuing leadership contest.

On Wednesday, Mr Duncan Smith was in bullish mood, insisting he "welcomed" the opportunity to clear the air, but warning that if his colleagues opted for a new leader, it would take time for him or her to learn the ropes.

He said the choice was between him taking the party to the next election as "a unified force", or the Conservatives plunging themselves "into a war of words" with a leadership challenge and "losing the opportunity to beat the government at their most critical and vulnerable time".

Mr Duncan Smith said he had ignored the continued vilification of his character in the media because he believed what he was doing was right.