An IRD spokesperson said the child- support contributions aimed to reflect the costs to parents of raising children and were based on international practice.
However, Parenting for Men Co-ordinator Dave Halligan, of Mount Maunganui, said child-support payments were a grievance for many. He said men he'd spoken to felt "disconnected" from providing for their children by not being able to pay the money directly to their kids.
"The vast, vast majority want to pay and give support but feel it's a real mechanical process. The IRD just rips it (the money) out of their bank account."
He said the amount required of parents who did not have full custody was crippling for some.
"It's assessed on your gross income and taken out of your net pay. I know there are some guys who set up a limited liability company and contract their wages through that. It means they're not paying PAYE. When they're paying PAYE, the IRD can see what their earnings are."
Family First NZ national director Bob McCoskrie said the child-support system had to be fair to both parents.
He said child support should be targeted at parents who abandoned their responsibility, or who were proved to be unsuitable to care for the children.
"Not at those who wish to maintain their responsibilities related to raising their own children," he said.
Mr McCoskrie said there was an issue with parents going overseas and avoiding their responsibilities, and children were the "ultimate losers" in this. Figures from 2008 showed nearly 13,000 liable parents lived overseas, yet this group owed one-third of the total debt.
In November last year, a Tauranga woman who asked not to be named said she'd been forced to use the services of the Tauranga Foodbank because of inconsistent child-support payments.
The mother, a 32-year-old Greerton office worker, told the Bay of Plenty Times she was a single mother to a 14-year-old boy and a 9-year-old girl. She worked 20 hours a week and supplemented her income with child support. The only problem was, the child support didn't always arrive when needed.
"I pretty much rely on my child support, which of course their dads never pay," she said.
"They're meant to pay monthly, but they don't and I doubt I'm the only one in that spot. You get your payment, go out and do a big shop-up, and if you don't (get your payment), you wait another month scraping by. It drives me insane and, really, I could live reasonably comfortably if they just paid their minimum ..."
An IRD spokesperson said the "majority" of child-support paying parents would default on their payments at some point. Most contacted the IRD when this happened. The Child Support Act put the onus on parents to advise the IRD of a change in circumstances.
Penalty payments were kept by the Government to offset administration of the scheme, and penalty write-offs were available for parents who made and complied with a repayment arrangement. Payments were calculated based on gross income rather than after-tax income.