The Government was urged to spend at least another £4bn on helping Britain's poorest families, in order to avoid missing its targets to cut child poverty.
The leaders of 53 children's charities, trade unions, faith groups and businesses told the Chancellor Gordon Brown that Labour's goal of halving child poverty by 2010 and abolishing it by 2020 would not be achieved on current trends.
The End Child Poverty group welcomed the lifting of 700,000 children out of poverty since 1997 but it marked the International Day for the Eradication of Poverty by warning that, while Britain was the world's fourth wealthiest nation, it had 3.4 million children living in poverty. In the EU, only Italy, Portugal, and Slovakia have higher rates.
Hilary Fisher, the group's director, said: "There is widespread concern that the Government must take action now otherwise they will fail their child poverty targets. We are concerned of complacency setting in and child poverty slipping further down the agenda."
In its annual report on poverty yesterday, the Government said that 40 key indicators were moving in the right direction, nine were broadly constant but admitted that seven were moving the wrong way.
Those indicators are life expectancy at birth; infant mortality rates; obesity among two to 10-year-olds; employment disadvantage for the lowest qualified; the education gap for looked-after children; the number of families in temporary housing and people contributing to non-state pension.
The Government put the number of children living in poverty at 2.4 million, a lower figure than End Child Poverty because it takes housing costs into account.
John Hutton, the Work and Pensions Secretary, said the Government had achieved an "impressive reduction" in poverty but admitted it needed to renew its efforts if it was to meet his child poverty targets.
He signalled a change of strategy under which the Government would try to encourage both parents back to work when a family is living below the poverty line. A review of its strategy that concludes later this year will consider whether more work incentives should be offered to couples through the benefits and tax credits system.
"We must now focus on families where one parent works but the family remains in poverty," said Mr Hutton. "Almost half of all children in poverty are in households in which at least one adult works. The majority of these are couple families."
He rejected criticism that the Government was complacent about the issue. "As a result of tax credits, benefit reforms and the minimum wage, the poorest families with children are now on average £3,350 per year better off," he said.
Last night, Mr Brown and Ken Livingstone, the Mayor of London, set aside political differences to launch schemes to use the 2012 London Olympic and Paralympic Games to permanently cut unemployment and child poverty in the capital.
The Chancellor told a reception for the London Child Poverty Commission: "Our thoughts are not just about those we have helped but the millions we have still to help not just out of poverty but towards their full potential. The Olympic and Paralympic Games are a great opportunity for us and I believe it will inspire today's generation of childrento reach their potential and achieve their aspirations."