More families need to be given seasonal grants to help children living in poverty, a charity has said.
The government missed the first target in its bid to end child poverty
It comes after a Save the Children survey of 1,500 British families found 60% did not have enough money.
About 500,000 children in the UK would be in unheated homes this winter and without essential items including warm clothing, the charity said.
Chancellor Gordon Brown has indicated that families on the lowest incomes may receive more help with fuel bills.
Two out of every three parents surveyed said they had been in debt, with one in 10 taking loans from doorstep lenders.
'Two annual grants'
Save the Children said only 16% of families surveyed said they could survive on benefits.
The study also suggests one out of every three low-income parents feels their relationship with their partner is under pressure because of money worries.
One out of every five surveyed said poverty also puts a strain on their relationship with their children.
Nine out of 10 parents interviewed said they often went without to make sure that their children had enough.
Nearly eight out of 10 - 77% - cited winter and Christmas time as the most difficult.
The charity has now called for two annual grants to help low-income families.
It claimed seasonal grants of between £100 and £200 - once in the winter and again in summer to help parents pay for back-to-school costs - could lift 440,000 children in the UK out of poverty.
Save the Children chief executive Jasmine Whitbread said: "It is outrageous that families in the UK are struggling to afford basic things like proper food or heating their home.
"The UK is a wealthy country yet we have one of the highest rates of child poverty in Europe.
"Gordon Brown must recognise that for the government to get back on track in its ambition to end child poverty, greater investment is essential."
Mr Brown said the government was committed to tackling child poverty, but said the problem required a number of solutions.
He told GMTV: "There's not enough people in work. We've got to help more people get into jobs, we've got to do more to help people out of child poverty with better benefits, and we will do that, and we continue to do that."
He said there were many "pressure points" throughout the year for families, and indicated he may offer help with fuel bills for certain households.
"For families there are different points in the year - there's Christmas, there's the birthday of the child, there's the summer holidays - all these are pressure points," he said.
"I think we'll do more on fuel bills because that's one of the pressure points for families, and I want to do more in getting books to children at Christmas."
The charity has estimated that an extra £4bn - 0.3% of GDP - is needed to ensure the government meets its next child poverty reduction target by 2010.
Ministers have already missed their first target for the eradication of child poverty, earlier this year.
Save the Children also wants all political parties to sign up to a target to eradicate child poverty by 2020.