Seasonal goodwill bypasses beleaguered Iain Duncan Smith

Sir Edward Heath's thinly veiled attack on Iain Duncan Smith today is the latest salvo in a Christmas barrage of criticism against the Tory leader.

The former prime minister's intervention on Europe – the issue that has caused the most bitter divisions in the Tory party – is certain to be seized upon by Mr Duncan Smith's internal adversaries.

Now senior Tories fear the sniping against the leader and the glaring lack of unity in the party will not stop until he steps down. Even after weeks in which the personal reputations of the Prime Minister and his wife, Cherie, have floundered because of claims surrounding their connections with the convicted fraudster Peter Foster and poll results showing a lack of faith in Tony Blair's government, Mr Duncan Smith has failed to capitalise on Labour's troubles.

Instead his opponents within the Tory party have continued to raise questions about his leadership and to plot against him. Even his supporters admit the first half of next year will be a crucial test and will determine his future.

One Tory source said Mr Duncan Smith was in "permanent deep trouble", adding that spring elections in Scotland, Wales and the English councils would be "the defining moment". Another said: "If he fails then, he'll have to go – assuming he lasts that long." But a senior backbencher predicted the sniping "will never stop". "I can't see how he can turn this one round," he said.

MPs and ordinary party members are worried that they are just "written off as irrelevant". One source said: "I think that's the biggest crisis we face because we are in front of an open goal and utterly failing to capitalise on it."

Season of ill will for Tory leader

17 December: Iain Duncan Smith wakes to the Conservatives' worst poll rating for four years. A Guardian/ICM survey puts Labour support on 41 per cent with the Tories down 2 per cent at 27 per cent – the lowest since November 1998.

18 December: Reports that Kenneth Clarke is ready to join the Tory right to oust Duncan Smith reignite the leadership rumours begun by Michael Heseltine's call for a Clarke-Portillo "dream ticket".

19 December: The press reports that he spiced up his Who's Who entry to include a stint at the University of Perugia. The truth is that he spent time at a language school nearby.

20 December: David Davis, the shadow Deputy Prime Minister, lets it be known he would run for the leadership – but only if Duncan Smith stood down. And critics seize on IDS's decision to add a second "I" to his name, elevating himself from plain old George Ian Duncan Smith. No wonder his own staff failed to recognise him at the Tory Christmas bash.

21 December: Ex-Sun editor Kelvin MacKenzie is signed up by Channel 4 for a programme in which the journalist promises he'll be "getting out the John Major shit bucket and pouring it all over Iain Duncan Smith".

22 December: Major Tory party donors call for IDS to stand down, claiming he is a "nonentity". A survey of Tory voters by IDS's aides said he was "unelectable, not normal, has no character and is patronising" to the less well-off.

23 December: Attempts to boost support with the promise of tax cuts descend into farce. IDS's announcement of a new year offensive is undermined – by shadow Chancellor Michael Howard.

24 December: Chris Patten, the former Tory chairman, accuses his party of having a "nervous breakdown" because of its "obsession" with Europe.

25 December: Even IDS's detractors have a day off.

26 December: They're back. The Liberal Democrats set up "hit squads" to unseat five senior members of the shadow cabinet at the next election.

27 December: IDS outlines his latest strategic thinking on the Today programme. His words are drowned out by Jenny Ungless, his former chief of staff, who attacks his failure to offer "positive alternatives" to Labour.

28 December: A MORI survey puts IDS's party on course to lose a further 20 seats at the next election.