George Osborne, the Shadow Chancellor, has distanced himself from Conservative “über-modernisers” and defended a decision to campaign on the issue of immigration.

Mr Osborne publicly revealed the tensions at the heart of David Cameron’s leadership in an interview on the eve of the Tory party conference in Blackpool.

As Gordon Brown intensified efforts to persuade Tory MPs to defect to Labour, the Conservatives’ election co-ordinator dismissed claims of a “lurch to the right”.

“I don’t take the kind of über-modernising view that some have had, that you can’t talk about crime or immigration or lower taxes,” Mr Osborne told The Spectator. “It is just that you can’t do so to the exclusion of the NHS, the environment and economic stability. I have always argued for a more balanced message, and that is what I hope you would see at this party conference.”

Conservative officials later insisted that Mr Osborne was not referring to any members of Mr Cameron’s inner team. But although his key target was Michael Portillo, it is understood that he also had Michael Gove, a key Cameron ally, and Francis Maude in mind.

Mr Osborne’s criticisms came as the party received a £1 million donation from a businessman angered by Labour’s failure to beat violent crime.

Dave Whelan, sports shop tycoon and chairman of Wigan Football Club, pledged to hand over the cash within 14 days if a general election is called. He said he had been particularly affected by the death of 11-year-old Rhys Jones, who was shot in Liverpool. The decision to discuss immigration last month divided Mr Cameron’s key allies. Some of those closest to the Tory leader believe it undermines his efforts to show the party has changed.

Mr Osborne spoke for the other camp when he insisted that Mr Cameron was right to say that immigration “has been too high”. He went on: “Immigration from Eastern Europe was 100 times – well, maybe 50 times – greater than the Government predicted it was going to be. So there was a complete failure to anticipate the impact on our public services, or indeed the impact on our economy.”

He added that although immigration has been a “broad benefit” to the country, it had put an “enormous pressure” on low-skilled Britons.

Mr Portillo declined to rebut Mr Osborne’s criticisms but his remarks threaten new in-fighting as Mr Cameron’s leadership faces its sternest test.

Meanwhile, Mr Brown has authorised a covert operation to find Quentin Davies a safe Labour seat to encourage other Tory MPs to switch sides. Mr Davies, elected as Conservative MP for Grantham & Stamford, was given a standing ovation at the Labour conference in Bournemouth.

A senior aide to Mr Brown hinted at more defections – possibly timed to cause disruption to the Tory conference. “Put it this way, it’s not just women who have been impressed with the start that Gordon has made,” he said.

Mr Brown himself issued a public appeal for defectors during a question-and-answer session at the conference. The latest recruit from the Conservatives was revealed as Judith Symes, who stood as a Tory candidate for Brighton Kemptown. The 43-year-old was on the Tories’ Alist before moving to Labour.

Patrick McLoughlin, the Conservative Chief Whip, is said to be ringing round Tory MPs asking them to identify Members of Parliament who are being targeted by Labour.

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