Almost half of single parents using the Child Support Agency (CSA) say they cannot afford to pay fees proposed to access the new child maintenance service, according to a new study.
The Gingerbread charity said its survey of 1,700 single parents suggested that thousands of children could go without vital money after the agency is wound down from next year and replaced with a new system which could cost £100 to access.
The charity said its findings countered Government assumptions that paying fees to use the new service were realistic options for most separated parents.
Gingerbread chief executive Fiona Weir said: "This shows the devastating impact that charging could have on the amount of child maintenance that will get through to children.
"If these findings were to be replicated across the whole CSA caseload, that could mean nearly 300,000 single parent families would go without child maintenance.
"Ever since these proposals were announced, single parents have been in touch with us in their droves to tell us the hardship they will face if they can no longer get child maintenance. We urge the Government to scrap these proposals."
A Department for Work and Pensions spokesman said: "We have committed to providing a far better service for families that is still heavily subsidised by the taxpayer.
"Our reforms will help both parents to take responsibility for their children and reach their own arrangements free of charge. The fact remains that the current system is not working well enough for children.
"Children must be at the heart of reforms. It is not helpful to use the CSA as a weapon between warring parents who could reach their own arrangements."