Gordon Brown has been accused of backing away from his pledge to eradicate child poverty.
A report from the Joseph Rowntree Foundation (JRF) found one in three children are still living in poverty, while MPs questioned the government's commitment to halving child poverty by 2010.
The JRF report found poverty had worsened over the past year, with nine of the 50 indicators used to measure poverty showing a decline.
The researchers said ministers must do more to tackle poverty if the government is to achieve its pledge of halving child poverty by 2010 and abolishing it completely by 2020.
Despite these ambitious targets, JRF found child poverty in 2005-06 had been higher than the benchmark set for 2004-05.
With half of all children in poverty living in working households, the report said the government must do more to help the working poor, including tackling low pay in the public sector.
Amid stalled progress so far, a report from the Treasury Select Committee has seriously questioned Mr Brown's commitment to increasing efforts to tackle child poverty.
After analysing this autumn's comprehensive spending review, MPs concluded there was no clear indication how the government plans to halve child poverty by 2010.
In particular, the cross-party committee of MPs criticised the government's plans to cut inheritance tax. It said the £3.5 billion this is expected to cost over three years would be better spent tackling children poverty.
Committee chairman John McFall said the government "may have drawn back from a whole-hearted commitment" to abolishing child poverty.
Mr McFall said: "The 2010 child poverty pledge should not be seen as an optional extra in the government's programme for the remainder of this parliament.
"The government must do more to make clear how it is to meet its target to halve child poverty by 2010 or face growing concerns that its commitment to the target is being watered down."
Welfare reform minister Caroline Flint insisted the government was still committed to making progress on poverty.
Ms Flint said: "As the JRF has recognised, a tremendous amount of progress has been made in improving the lives of people over the last 10 years - 600,000 children and over a million pensioners have been lifted out of poverty and a million fewer people are on out-of-work benefits.
"But we know that more needs to be done and we firmly believe that sustainable work is the best way out of poverty."
She added: "We are taking action to rip up sicknote Britain, establish a new cross-government child poverty unit and ensure more people get the skills and support they need to access the two-thirds of a million job vacancies that exist on any given day."