Proposed changes to the child support system are being labelled too complex for parents and too expensive for taxpayers.
The changes include a new calculation formula to reflect parents' levels of care arrangements and updated payment, penalty and debt rules for child support.
The Social Services Select Committee has recommended the bill become law, but has advised it should not be implemented until April 2014 to give the Inland Revenue Department time to prepare its systems.
The Labour and Green parties are raising doubts about whether the IRD's systems are up to it, considering recent privacy lapses.
But Revenue Minister Peter Dunne says the IRD can cope with the changes and it has plenty of time to prepare.
He says the Greens' concern that parents will need an accountant to work through the changes is "hysterical claptrap".