The Child Poverty Action Group (CPAG) said that the cost of raising a child to the age of 18 has gone up by 4% over the last year.
But the value of benefits for families and children only rose by 1%, and child benefit did not rise at all, tightening the squeeze on living standards.
At the same time minimum wages rose 1.8% and average earnings by 1.5%, making it harder for parents to provide a decent standard of living for their families.
Alison Garnham, chief executive of Child Poverty Action Group, said: "This research paints a stark picture of families being squeezed by rising prices and stagnant wages, yet receiving ever-diminishing support from the Government over the course of the last year."
The report, co-funded by the Joseph Rowntree Foundation, found it cost about £160 a week to raise a child, including child care costs and housing.
The basic cost for a couple to raise a child over 18 years was £81,772, or £148,105 including rent, child care and council tax, with those figures rising to £90,980 and £161,260 respectively for a lone parent.
Many low-income families have also seen cuts in housing support, such as the spare room subsidy, or "bedroom tax", and many non-working families are now required to pay council tax.
The report also found that families on out-of-work benefits faced an even greater shortfall of income, with couples receiving only 58% of what they need to meet minimum costs, and lone parents getting 61%.
The CPAG also said the introduction of the universal credit system in October would bring mixed results, with both couples and lone parents working full time on a minimum wage being left some way short of an acceptable living standard.
Ms Garnham called on the government to "renew our national commitment" to children before the next election.
She said: "Every parent knows it's getting harder to pay for the essentials their children need, and they don't feel like politicians see them as a priority. Child benefit and child tax credit have been cut at the very time families need them most. Families are getting worse off and parents know it.
"If every child in Britain can grow up healthy, well-educated and an active participant in their community, we all benefit from a more prosperous economy. This was well understood by the post-war generation who prioritised universal benefits for all children despite being much deeper in debt than we are today.
"As we move towards a 'living standards election', now would be a good time to renew our national commitment to all our children."
Katie Schmuecker, policy and research manager at the Joseph Rowntree Foundation, added: " The task of making ends meet for families with children has always been hard, but is getting harder, and balancing family budgets has become a perilous and delicate act for hard-pressed parents.
"Flatlining wages, cuts to benefits and tax credits and the rising cost of essentials is creating a growing gap between income and needs.
"The next election is likely to be the first since the 1930s where living standards are lower than the last poll. All parties must go to the country with policies and a commitment to help the prospects of low-income families.
"The risk and costs otherwise are enormous. Child poverty costs the Treasury £29 billion a year - a price we can scarcely afford to pay, particularly in the current economic context."