Duncan Smith faces new challenge from his party

Iain Duncan Smith faced growing pressure last night to submit himself to a vote of confidence among Tory MPs.

Derek Conway, a former whip, made the demand as he criticised the Tory leader's "treacherous" behaviour during the years of John Major's government. Conservative high command, braced for fresh claims over public cash paid to Betsy Duncan Smith, revealed its jitters yesterday when an interview with Theresa May, the party chairman, on The Politics Show on BBC 1 was cancelled.

Jeremy Vine, who presents the programme, said that her appearance had been vetoed "under instructions from above". Mr Conway, interviewed on GMTV, joined Sir Patrick Cormack, a member of the executive of the 1922 Tory backbench committee, in saying that Mr Duncan Smith would win a new mandate from his MPs.

He said: "I think it's in his own interests and in the interests of the party that he should. Because part of the problem with the electoral system we've got in the Tory party [is] that Iain was elected with only a third of MP support."

Mr Conway said that Mr Duncan Smith had to "lance the boil" of discontent within Tory ranks. "There's a growing feeling of 'it's got to end, we've had enough of this, it's got to end one way or another'," he said. He added that John Major had experienced a similar situation during his administration. He said: "I was involved in John Major's administration when he went through the 'back me or sack me' episode, because at the time backbenchers like Iain Duncan Smith were being so very, very difficult, indeed treacherous. And therefore the Prime Minister eventually had enough and said 'I can't go on like this, you've got to back me or sack me'."

Sir Philip Mawer, the Parliamentary Commissioner for Standards, will today continue his investigation into payments to Mrs Duncan Smith. Vanessa Gearson, a deputy director at Conservative Central Office, may make a brief public statement. However, it is understood that she will not discuss details of her submission to Sir Philip about the allowances paid to the Tory leader's wife.

Mark MacGregor, the party's former chief executive, who had a public falling-out with Mr Duncan Smith, will also give evidence today. The shadow Foreign Office minister, Alan Duncan, said that Tory divisions were "exaggerated and subsiding" and that Mr Duncan Smith should be allowed to continue as leader. He also said there was no point in Mr Duncan Smith submitting himself to a voluntary vote of confidence. "I say stick with him and let's concentrate our efforts on advancing policies and trying to position the Conservative party to being a credible opposition to Labour," Mr Duncan told Sky TV.

Oliver Letwin, the shadow Home Secretary, said that no leader ever had "100 per cent support from everyone all the time". He told BBC 1's Breakfast with Frost that the Conservatives had to do better than in the past few weeks but senior Tories were not "all rowing".