The Labour Party faces a downturn in union funding unless its next leader renounces the Blairite strategy of wooing right-of-centre voters, GMB general secretary Paul Kenny has claimed.
In what appeared to be a warning to David Miliband, the bookmakers' favourite, Mr Kenny said Gordon Brown's successor at the helm of the party must not offer "more of the same".
The GMB publicly endorsed the shadow foreign secretary's younger brother, Ed, who has made clear he will focus on re-engaging core supporters and those who have shifted their allegiance to the Liberal Democrats.
David Miliband is advancing a more centre-ground approach, insisting Labour should seek to appeal to the kind of broad coalition that Tony Blair attracted in 1997.
Labour, which is in financial dire straits following the general election campaign, is largely reliant on the unions to keep it afloat. The GMB gave almost £1.5 million in the first half of this year.
In an interview with The Times, Mr Kenny also suggested Ed Balls, the shadow education secretary who is also running, would need to adapt his platform to win union favour.
Asked whether the GMB would withdraw funding for Labour if shadow energy secretary Ed Miliband did not win, he replied: "If the new leader offers us more of the same, many unions - including our own - would have to consider where we are at.
"Ed Balls and David Miliband represent where we've been. They are not without talent. I would not rubbish them. But if the direction of the party went off chasing right-of-centre ground..."
He added: "Ed Miliband is not ashamed of Labour's core values. It's not about a big society. It's about a fair society."
With ballot papers set to go out next week, Ed Miliband appears to be the closest challenger to his elder brother. As the stakes have risen, the differences between them have grown in recent days.
