The system for ensuring non-resident parents pay towards the upkeep of their children has amassed nearly a billion pounds in arrears, figures showed yesterday, leading to calls for a "root and branch" review of the Child Maintenance Service (CMS).

SNP MP Marion Fellows raised the issue at Prime Minister’s Questions, as figures showed arrears under the CMS scheme rose by £7.4 million in a 15 months.

While the agency is meant to ensure parents take responsibility for their children, Ms Fellows said its bark was worse than its bite.

Calling for a crackdown on the enforcement of payments, she said "children are living in poverty because of a lack of maintenance payments."

The latest DWP figures show CMS arrears rose from £966 million to £973.4 million between December 2018 and March 2019 – an increase of £7.4 million.

Between the same months, £58.5 million was owed under CMS’s Collect and Pay service– where CMS monitor and pursue collections – but only £40.6 million was paid.

A third of all cases assessed under Collect and Pay have paid nothing while the remaining 67% can only be guaranteed to have “paid some maintenance”.

While the UK Government introduced new measures to put pressure on 'deadbeat' parents, such as confiscating passports, in December, the DWP predicts that only 20 passports will be confiscated in the first year.

Meanwhile the UK Government wrote off £1.2 billion of historic CSA arrears last year, and is seeking to wipe out an additional £1.3 billion instead of moving thee arrears to the new CMS.

Responding, Theresa May said the government wanted to ensure parents "normally, it is fathers, but sometimes it is mothers", take their responsibilities seriously. She said the system was working better, but that it was a difficult problem which previous government had also struggled to get right.

Mrs Fellows added: “The UK Government has to crack down on enforcing payments to ensure children receive their maintenance rights. New powers are welcome [and] confiscating passports is a start, but it isn’t delivering maintenance payments.

When charities like Gingerbread say maintenance can lift one in five children out poverty, there needs to be a will to act on the evidence. We have heard stories from parents that the Child Maintenance Service is rife with problems, from calculations to enforcement to customer service. A full root and branch review is needed to ensure fairness for both parents, but ultimately it is the children who are losing out..”