The new charges apply in every case where a parent has asked the Child Maintenance Service to help collect maintenance from a paying parent after they have failed to make contributions towards the upbringing of their child. Resolution is concerned that the introduction of the fees, in which 4% is deducted from the payment which is received by the with care parent and 20% is added to liability for the other parent, may put many parents off the Child Maintenance Service entirely.

Resolution believes that the charges will disproportionately affect vulnerable families, since no one chooses the Collect and Pay system if they can reach a private agreement. Already many separated couples find managing two households is financially difficult, and this extra fee, according to Resolution's Stephen Lawson, "may be the straw that breaks the camel's back."

Single parent support group Gingerbread has similar criticisms, saying the new charges take money from those meant to receive it -- children. Gingerbread's latest research shows that two in three working single parents find their finances to be at best a constant struggle.

According to Gingerbread slightly over half of separated families (52 percent) currently have child maintenance agreements in place. The charity is concerned impeding case closures and the charges may mean that even fewer children receive the support they require. The impact assessment produced by the Government predicts 400,000 families will stop receiving maintenance due to the charges.

While there are less than 60,000 parents enrolled in the new CMS, the Government has begun the process of closing the existing CSA cases and suggesting parents try and arrange a private agreement before they open cases with the new service. The CSA currently has upwards of 1 million cases, and all of these will be closed inside the next three years.