Staff at the failed Child Support Agency were paid £25m in bonuses over five years, government figures reveal.
The CSA has been criticised by parents
In 2006, when the government announced the CSA would be replaced, £4m was paid out in bonuses, it was revealed in a written Parliamentary answer.
The CSA is being abolished after failing to collect £3.5bn of child maintenance payments.
For the Tories, Philip Hammond said it would come as a shock to the 1.4m families using the CSA.
Mr Hammond, the shadow work and pensions secretary, said: "Families trapped in the CSA will rightly ask whether this money could have been put to better use in a system where £3.5bn debt remains uncollected and 250,000 cases languish on a backlog."
'Slap in the face'
Details of the bonuses were revealed in a written answer by Trade and Industry Secretary Alistair Darling.
It showed that, since 2001, bonuses totalled £25,661,000.
For the Lib Dems, David Laws MP said: "It is frankly ridiculous that while the CSA fails to collect over £3.5bn of unpaid maintenance, it sees fit to reward its employees with £25m worth of bonuses."
He added: "Finding out that employees have been given bonuses for their work at this time is a slap in the face for the tens of thousands of families living in poverty due to its incompetence."
But a spokeswoman for the Department for Work and Pensions said the bonus scheme had been agreed with the unions and rewarded individuals' hard work.
"CSA staff are of course eligible to be recognised in this way," she said.
"The CSA's well-documented problems stem from the design of the system introduced in 1993, but staff should not be punished for them."
Last year the government announced that the CSA would be axed, after years of criticism about issues from its failure to collect maintenance payments to accusations of snooping and unfair settlements.
The Child Support Bill aims to replace it with a smaller body and a simpler way of collecting child maintenance.
The Child Maintenance and Enforcement Commission will be able dock wages and withdraw the passports of absent parents.
But the Conservatives and Lib Dems accuse the government of delaying the move and say reform is needed now.