A major inquiry into spending on children in Wales has been told it is impossible to determine whether there is enough investment to help the poorest gain good qualifications and escape the poverty trap.
Save the Children said the Assembly government had failed to provide enough evidence that targeted funding was helping needy children to achieve against the odds.
The charity also said that Wales was lagging behind England in helping disadvantaged children, despite child poverty being top of the agenda since devolution.
Save the Children also hit headlines this week by suggesting that city bankers should waive their bonuses and donate the money to a good cause - lifting a quarter of a million children out of poverty.
Eleri Thomas, head of Save the Children in Wales, said: "How is it possible to argue that this country can't afford to tackle child poverty when banks funded by the taxpayer are giving out pound;2 billion in bonuses?"
Giving evidence to the children and young people's committee earlier this week, Anne Crowley, Save the Children's assistant director for policy and research, called for the introduction of a national budget for children in Wales to make the government more accountable.
"In terms of what's being spent on children living in poverty in Wales, it's very difficult to find out . whether there's money being put where the rhetoric is. There needs to be more transparency and visibility," she said.
She added that while moves had been made to tackle child poverty in Wales - particularly through education - progress was "very slow", especially compared with England, where targeted schemes had been shown to work.
Her damning evidence was given before the publication, next month, of a Save the Children report into child poverty in the UK.
Last November, the cross-party committee came up with 27 recommendations to improve the life chances of deprived children, including poverty training for every teacher and universal free school meals. But members of the committee remain "unconvinced" that their proposals will be acted upon.
Professor David Egan, director of the Institute for Applied Education Research at UWIC in Cardiff and a former political adviser, agreed that there were still widespread concerns in Wales over whether money was being spent effectively or where it was most needed.
Save the Children is poised to launch a major government-funded investigation into how to narrow the gap in attainment between deprived and affluent pupils.
It is hoped the charity's findings, due in September, will feed into the school effectiveness framework, a scheme aimed at spreading good practice to poorly performing schools in Wales.
Although the number of disadvantaged children has declined from 35 to 29 per cent since 1998-99, around 170,000 youngsters still live in poverty.
Statistics show that children who are eligible for free school meals generally perform below average at all key stages.
GCSE results are still strongly linked to deprivation - the higher a school's free meal entitlement, the greater the number of pupils who fail to obtain five or more good GCSEs.
In his recent annual report, Dr Bill Maxwell, the chief inspector, said that schools were failing to tackle poverty sufficiently.
An Assembly government spokesperson said it had begun reviewing its existing child poverty policies and a new strategy would be launched later this year.
She said: "Tackling child poverty remains a priority for the Assembly government and we have made clear our commitment to supporting the UK government's 2010 and 2020 targets."
She added that the government would respond to the evidence presented to the child budgeting inquiry after the committee had published its findings.