Labour modernisers have warned Tony Blair there is a "void" at the heart of his New Labour project because he has lacked the courage to force through radical reforms.
The Labour Renewal group, which has close links with some cabinet ministers, has declared the Government has "no sense of purpose" and many party members feel it despises them.
The surprisingly strong attack came as Frank Field, the former social security minister, warned that the line taken by William Hague, the Tory leader, on immigration, law and order and Europe was more in tune with public opinion than Labour's.
Mr Field said, in The Spectator magazine, that the election of Ken Livingstone as Mayor of London could herald a break-up of Labour's vote. He warned that the disengagement of long-time party supporters had grown to "a tidal force" at last week's local elections.
Renewal, a Blairite group close to ministers such as Clare Short, Mo Mowlam and David Blunkett, fires its broadside in this weekend's edition of its journal.
"In making ourselves electorally successful, we have left a void at the heart of Labour," writes Neal Lawson, a former aide to the Chancellor, Gordon Brown, and the journal's managing editor.
"There is a lack of narrative, purpose and meaning which translates into a lack of coherence and confidence in government. The central problem is that there is no overarching sense of purpose. Too often we choose economic efficiency over social justice; and it can seem as if we are practising the discredited trickle-down politics of the right."
In a direct challenge to Mr Blair's "big tent" policy of wooing Conservatives and Liberal Democrats, Mr Lawson writes: "Our challenge is to deepen our political roots, not to herd a flock of nervous sheep within the tent of 'one nation'. Satisfying no one for fear of offending anyone is unsustainable. We cannot continue being all things to all people.
"The terror of offending paralyses us. Too often we start something and then it is let slip when faced with the hard choices that any really meaningful political position entails."
He accuses Mr Blair of not following through his attack on the "forces of conservatism" last autumn because he offended the Daily Mail and The Daily Telegraph newspapers "Instead of finally chucking someone out of the bloody tent, we backed down. We did not want to define the enemy," Mr Lawson says.
He calls for Labour to openly pursue a policy of redistributing wealth instead of doing it by stealth. By ducking the argument, Labour would never win the debate.
Without a sense of purpose, Labour supporters would stay at home in future elections. "Too many members and activists feel despised and alienated from 'their government'," he says.
Warning that time is short, Mr Lawson predicts that Labour will run out of steam in two or three years unless it pursues more radical policies now.
"The well of reasonable excuses for lack of radical progress has run dry," he says.Reuse content