The government is committed to eradicating child poverty by 2020
The number of children living in poverty has risen for a second year, a government report says.
The government called the rise in poverty levels "disappointing" and the increase may threaten its target of halving child poverty by 2010.
The number of children living in poverty rose by 100,000 in 2006-2007 to 2.9 million before housing costs.
Pensioner poverty increased for the first time since 1998, rising by 300,000 to a total of 2.5 million.
The number of children and pensioners in poverty is greater once costs such as rent and mortgages are taken into account.
"This is a disgrace. We are watching more and more pensioners drop further below the poverty line," said Mervyn Kohler of Help The Aged.
Kate Green, the head of the Child Poverty Action Group, said the government should spend at least an extra £3bn a year on benefits and tax credits to meet its promises on child poverty.
"Ministers cannot take a holiday from their promise to end child poverty, or this is what happens," she said.
"Every year progress must be planned, invested in and achieved."
The main measure of relative poverty used by the government is the number of people living in households with income 60% below the median household, with the poverty line adjusted for family size.
The Institute for Fiscal Studies (IFS) said the government would have to reduce child poverty by 300,000 a year for the four years following 2006-07 to meet its target of halving child poverty by 2010-11.
POVERTY LINE (WEEKLY INCOME BEFORE HOUSING COSTS)
Couple, two children aged 5 and 14 - £346
Lone parent, two children aged 5 and 14 - £271
Childless couple - £226
Single individual - £151
It predicts the number of children in poverty before housing costs are taken into account will fall by 700,000 to 2.2 million by 2010, missing the target by 500,000.
Additional spending on child tax credit of around £2.8bn would be needed to for the government to have a 50:50 chance of meeting the target, the IFS said.
"Further increases in poverty and inequality will not be welcome news to the government," said David Phillips, IFS research economist.
The Secretary of State for Work and Pensions, James Purnell, said the government had made significant progress on child and pensioner poverty.
"Had the government done nothing other than simply uprate the tax and benefit system, we estimate there would have been 1.7 million more children and 1.5 million more pensioners in poverty today," he said.
After housing costs were taken into account, the number of children living in poverty rose by 100,000 to 3.9 million.
Since 1998, the number of children living in official poverty has fallen by 600,000 before housing costs and by 500,000 after housing costs are taken into account, the report said.
The government is committed to eradicating child poverty by 2020.
Professor John Hills, the head of the Centre for Analysis of Social Exclusion at the London School of Economics, said the figures were "disappointing if unsurprising".
"In years when the government takes action through taxes and benefits to help those on low incomes, the poverty figures improve," he said.
"In the period the figures released today cover, there were not many initiatives to help those on low incomes."