Single parents in Northampton are owed more than £7 million in child maintenance arrears, according to figures obtained under the Freedom of Information Act.
Parenting charity Gingerbread has released the findings of a study into the payments made between parents who have separated.
The figures show the Child Support Agency, which handles the transactions, has failed to collect around £4 billion nationally that single parents are entitled to .
The Government is currently closing the CSA and all of its arrears are being transferred to the new Child Maintenance Service (CMS).
But that means parents with children who have a CSA case outstanding will have to reapply to its replacement, the CMS if they want their arrears collected.
In Northampton, single parents are owed £7.4 million from the scheme, which works out at an average of £2,064 per family, according to Gingerbread.
The charity's chief executive, Fiona Weir, said: “Bringing up children costs money – they need clothes, food and a warm home – and both parents have a responsibility to contribute financially.
"The failure of the CSA to collect these millions of pounds of child maintenance means children are going without and single parents have been left poorer. Child poverty in single parent families is set to double in the next four years, so it’s even more essential that this money is collected."
Across all the constituencies in Northamptonshire, parents are owed a total of £29 million, the figures show.
While Northampton parents are owed the most, families in Corby are owed £5.6 million and Wellingborough £5.1 million.
Gingerbread says that as the CSA winds down, the agency is doing "even less to collect on the huge debts that have accrued" as the amount it collects per case has dropped by £35 since 2012.
The charity is calling on people to write to their local MPs calling on them to back its campaign to improve the child maintenance system, and is asking the Government to take action to collect unpaid maintenance.
To do so, folow the links from gingerbread.org.uk