Absent parents should make their child maintenance payments directly from their salaries or bank accounts, a committee of MPs has recommended.
They found the Child Maintenance and Enforcement Commission cost 50p for every £1 it collected and had failed to collect £3.8bn in payments due.
The Work and Pensions Committee called on the government to make the child support system more efficient.
The commission replaced the much-criticised Child Support Agency.
The committee found that many separated parents did not receive regular maintenance for their children and in some cases did not get payments at all.
Officials can take money directly from those who fall behind but the committee said direct payments from bank accounts or salaries should be required in all cases.
The government has said it wants to encourage separated parents to come to their own voluntary arrangements.
But its plans to charge a fee and call in officials to collect the payments of couples who cannot reach such an agreement were criticised by the MPs.
They also said the new agency still had operational weaknesses.
Committee chairman Anne Begg said the current system could easily be improved.
She told the BBC: “There are many non-resident parents who already set up a mechanism, usually direct debit, to make sure their children get the money that they’re entitled to.
“What we want to see is this widened so that everyone has an obligation to make sure there is some payment in process which is regular.”
A Department for Work and Pensions spokeswoman acknowledged the agency was not working well enough for children and said the government would give its full response in due course.
Last month, Prime Minister David Cameron said absent fathers should be “stigmatised” by society in the same way as drink-drivers.
However, he was criticised by charity Gingerbread which said government proposals to charge people in need of state help to obtain child maintenance payments would make life harder for single parents.
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