A bitter feud has broken out between US political strategists who helped Labour to three general election victories

A pair of US political strategists who helped Labour to a hat-trick of general election victories are conducting a public feud over claims that the party was hoodwinked by bogus polling into a disastrous last election.

Stan Greenberg, who worked on all three of Tony Blair’s campaigns, has accused his rival Mark Penn of using rigged polls that put Labour at risk by telling the leadership only what it wanted to hear.

Mr Greenberg wrote memos to Mr Blair and Gordon Brown after the election that “put on paper in an inescapable way my outrage at the polling and the banal strategy that followed from it”. He described the research as “unprofessional and lacking in methodological rigour” as well as “biased, self-deluding and overly optimistic”.

He claims that Mr Penn’s polling consistently showed Labour with landslide leads in the 2005 campaign while his own surveys in marginal districts more accurately predicted a significantly reduced majority.

He also accused Mr Penn of being fixated with the emergence of “soccer moms” in the US, which in Britain he transposed into “married mums” — even though three quarters of the lapsed Labour voters in the marginal seats did not have children at home.

Mr Greenberg — who has returned to work for Mr Brown for the past couple of years — warned that the “sense of betrayal” felt by many Labour voters had threatened the party’s ascendancy even before Britain supported the US in a deeply unpopular war in Iraq.

Mr Penn, who has been criticised widely for his role as chief strategist in Hillary Clinton’s failed presidential campaign, says the attacks are the product of sour grapes. In retaliation, he has published an effusive letter from the former Prime Minister expressing gratitude for “solid, sensible advice, with real insight and creativity” in the 2005 election.

The acrimonious exchanges in a series of interviews and internet articles this week have caused embarrassment on both sides of the Atlantic, shed fresh light on the ever-turbulent relationship between Mr Blair and Mr Brown and shown just how far Labour has relied on expertise from US Democrats.

Mr Greenberg, who has just published Dispatches from the War Room, writes of Mr Blair: “When Iraq looked broken, along with public trust, he was depressed and prepared to pass the torch to Brown. My work in this critical period showed him a road back, but he didn’t take it. It required acknowledgement of mistakes and independence from Bush, both of which I now understand conflicted with his surety about his course.”

Instead, the former Prime Minister listened to advice from Bill and Hillary Clinton who “called repeatedly to urge Blair to run again”. They also pressed him to employ Mr Penn, who had eclipsed Mr Greenberg as the Democrats pre-eminent pollster.

Writing on Pollster.com Mr Penn has defended his surveys as “extremely accurate” and suggested Mr Greenberg was, by this stage, working for Mr Brown’s interests. “We never predicted a landslide. Most of our polls showed Labour and Tories within 4-5 points. It was Stan’s predictions of a loss that proved inaccurate.”

Caught in the middle is Lord Gould of Brookwood, Mr Blair’s personal pollster who once went into business with Mr Greenberg before falling out with him over Mr Penn’s arrival in 2005. He said: “It is politicians and leaders who decide, who make successful campaigns, and build great political projects. When the final histories are written, it is not Stan’s or Mark’s or my view that will matter.”

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