Walkout by top aide undermines Duncan Smith

Iain Duncan Smith's plans to launch a political fightback at the Conservative Party conference in two weeks were in disarray yesterday after infighting between Tory factions claimed another victim.

The sudden resignation of Dominic Cummings, the Tory leader's director of strategy, is the latest episode in a battle between modernisers urging radical change and traditionalists.

Mr Cummings, 30, had appeared to be winning a power struggle between the "mods and rockers" when David Davis was ousted as Tory chairman in July. Mr Cummings had warned Mr Duncan Smith that Mr Davis was a "huge roadblock" to his plans to modernise the party by changing its policies and image.

The civil war erupted in June when Mr Cummings told The Independent with typical candour that the Tories should not lead the campaign against the single currency because they were "about the only thing less popular than the euro".

Mr Davis disowned Mr Cummings publicly but Mr Duncan Smith backed the youthful adviser he had headhunted from the anti-euro Business for Sterling group, even though he was not a member of the Tory party.

The Tory leader also took Mr Cummings' advice on Mr Davis, demoting him in a messy reshuffle while the chairman was on holiday. Allies of Mr Davis vowed to take revenge on Mr Cummings. Apparently, though, there is no blood on their hands, and Mr Cummings walked rather than being pushed. He is planning to spend several months abroad, possibly in California or central Asia.

Mr Cummings had been increasingly frustrated at the slow pace of modernisation. After persuading the Tory leader to portray the party as on the side of "vulnerable people", he was keen to see more flesh on the bare bones of party policy. He argued that the Tories needed their equivalent of Tony Blair's decision to end Labour's support for Clause 4. One option was for the Tories to drop support for Section 28, which bans local authorities from promoting homosexuality. But that was a step too far.

The dispute apparently climaxed over how far the Tories should go at the Bournemouth conference. "It's all in a state of flux; there has been a battle-royal," an insider said. The departure of Mr Cummings is a sign that caution will prevail.

With his open-necked shirts and north-east accent, Mr Cummings was never accepted by the traditionalists, led by Mr Davis and the shadow Chancellor, Michael Howard. "He was a young man in a hurry," said a senior Tory. But for some Tory colleagues, Mr Cummings was a breath of fresh air who could put the party back in touch. "Losing him is a tragedy, a victory for the dark forces," a shadow cabinet moderniser said.

Since July, Mr Duncan Smith has lost his party chairman, his director of strategy and his chief of staff, Jenny Ungless. The chaos has fuelled a whispering campaign against Mr Duncan Smith, who could find himself among the "vulnerable" after the council elections in May. A Tory MP said: "We should have got rid of William Hague halfway through the last Parliament but we carried on sleepwalking to electoral defeat. We won't make the same mistake this time."