One in 10 of New Zealand fathers may be paying child support for children who are not theirs, say men's groups.
Tax collectors confirm that payments have been stopped and money refunded after men proved that the child they were supporting financially was fathered by someone else.
The Inland Revenue Department national child-support manager, Martin Scott, said there "have been cases where men have disputed paternity and DNA tests show they haven't been the father."
The department did not record the number of cases where child support was stopped but Mr Scott said several men appealed to the Family Court to challenge the department each year.
The president of the North Shore-based national organisation the Men's Centre, Mark Rowley, said Australian research indicated that 10 per cent of children were raised by men who were unaware that they were not the biological father. British research suggested it might be 20 per cent.