Labour needs a new vision on tackling inequality because its current approach is too "scattergun", the architect of the Blairite Third Way has said.
Left-wing critics say New Labour has not done enough for the poor
Lord Anthony Giddens praised the government's "real achievements" on redistributing wealth - despite the criticisms of the "Old Left".
But he urged ministers to give the same commitment to cutting inequality as they had given to public services.
Top earners should not be ignored but top tax rates should not rise, he said.
His words come amid reports that Tony Blair is planning a major speech next week on cutting the welfare benefits bill.
Lord Giddens' lecture at the London School of Economics was in memory of Marxist academic Ralph Miliband, whose son Ed, a key Treasury adviser, was in the audience.
Left-wing activists have attacked New Labour for failing to do enough on reducing the gap between rich and poor.
But the former LSE director said: "It is not true to say New Labour have not been trying to do something about inequality."
Blair has promised to get more people off benefits and into work
There was now essentially full employment, next year's targets for cutting child poverty should be met, poor pensioners had been helped and the lowest 10% of income earners were 8% better off in 2003 than in 1997, he said.
Rebutting the criticisms of many of the "traditional Left", Lord Giddens said: "This Labour government is the first Labour government to actually affect redistribution rather than just talk about it."
Despite his praise, he suggested many people believed New Labour still lacked vision on tackling inequality.
He continued: "New Labour should make a commitment to a renewed egalitarianism...
"There is something out of kilter to New Labour's perspective. It has given so much commitment to public services but there is no parallel integrated commitment really to secure a more socially just society."
Lord Giddens said that vision should not be the "Old Left's" remedies of higher tax rates, more regulation in markets and investing in unreformed public services.
Giddens says it's hard to make sense of the vast range of policies
Securing economic growth was essential for tackling inequality, as recognised by Chancellor Gordon Brown, he stressed.
And it would be difficult to find policies that were both electorally feasible and which did more than already achieved.
But he said the government's problem in articulating a vision of social justice "comes from the scattergun nature of their policies".
Pointing to the vast range of anti-poverty initiatives, Lord Giddens said: "It has so many policies that it's very hard to make sense of them."
Ministers also had to think hard about the limits of the policies already in place, he said, asking whether more needed to be done for those unable to work, for example.
There needed to be more work too on reducing tax for the poorest groups, he said.
The Liberal Democrats have proposed a new 50% tax rate for earnings over £100,000 to raise £5bn.
But Lord Giddens argued it would raise a relatively small amount of money - about £3.5bn -while giving Conservatives a new avenue of attack.
He proposed more clampdowns on tax avoidance schemes among top earners and encouraging greater civic responsibility, perhaps through tax credits for philanthropy.
Powers for shareholders to have a say on executives' salaries could also be taken further.
Lord Giddens urged Labour to "gulp" and at least look at the interaction between the public and private sectors.
He pointed to the way millionaire Peter Lampl had funded a private school in Liverpool to be able to admit pupils only by ability - whatever their ability to pay fees.
The scheme has, however, prompted fears that state schools could lose their brightest children.
Meanwhile, the Daily Mail reports that Mr Blair will deliver a speech next week to flesh out his Labour conference vow to increase the numbers moving from benefits into work.
Downing Street refused to confirm the reports.