The government aims to eradicate child poverty in the UK by 2020
Ministers have admitted that meeting the government's aim of halving child poverty would be "very difficult" after new figures revealed no change.
Statistics show numbers of children in poor households - defined as those on less than 60% of the mid-point income - stayed the same between 2006 and 2008.
Campaigners accused ministers of breaking their pledge to halve child poverty by 2010 - a target set in 1999.
The government said it was working hard to put the rate "back on track".
The latest Department of Work and Pensions figures for households below average income show there were 2.9 million children living in relative poverty between 2007 and 2008 before housing costs were taken into account.
This is unchanged from the figures released last year for 2006/7.
Children's Minister Beverley Hughes admitted that given the current difficult economic climate, "meeting the 2010 target is very difficult" and that it was "very difficult to model the impact of the recession on child poverty".
However, the government had taken "strong prescriptive actions" to put rates "back on track", she said, and expected the effects to be seen between 2008 and 2010.
HOW POVERTY IS MEASURED
Relative poverty refers to households whose income is less than 60% of the median for similar households
The government and charities use two figures - before housing costs (BHC) and after housing costs (AHC)
AHC measures relate more closely to actual living costs and usually result in higher numbers classed as being in poverty
Source: Joseph Rowntree Foundation
She added: "The government is committed to supporting families and we are equally committed to ensuring every child, whatever their background, has the best possible start in life.
"Our determination to end child poverty by 2020 is as strong as ever and we are legislating to enforce that commitment."
The official statistics also showed there was no change in the number of pensioners judged to be living in poverty.
Some 2.5 million were living below the poverty line between 2007 and 2008 - the same as between 2006 and 2007.
But there was a rise in the number of working-age adults suffering financial hardship. Those living in poverty rose from 5.4 million between 2006 and 2007 to 5.6 million between 2007 and 2008.
Although ministers said this rise was partly due to an increase in the working population.
After housing costs were taken into account, the statistics showed there were four million children, two million pensioners and 7.5 million people of working age in poverty.
Overall, the report found there were 11 million people living in poverty in the UK - a figure that has risen by 300,000 since 2006.
Colette Marshall, UK director of Save the Children, said it was clear ministers were going to miss the government's own child poverty targets.
"The government has clearly broken its promise to lift up to three million children out of poverty in the UK," she said.
"Today's figures show that the government will fall well short of its 2010 target to halve the numbers of children living in poverty."
The Joseph Rowntree Foundation said allowing child poverty levels to continue costs the UK £25bn a year, while the Institute for Public Policy Research said it was "very disappointing".
The charity Oxfam said it was "alarmed" by the overall rise in poverty.
Theresa May, shadow work and pensions secretary, described it as a "tragedy" that the number of children in poverty was not being reduced.
"The government needs to wake up and get a grip of this problem. Simply relying on means-tested benefits to address the symptoms of poverty is unsustainable.
"Instead we must tackle the root causes of poverty, such as educational failure, family breakdown, drug abuse, indebtedness and crime."
However, Financial Secretary to the Treasury Stephen Timms said the government had made progress since 1997 through the introduction of tax credits and the minimum wage.
"The steps the government has taken to support the economy right now will help families and individuals, including a temporary cut in VAT worth over £20 a month on average for a household and an increase to the personal allowance worth £145 this year for 22 million basic-rate taxpayers, for example," he said.