During an interstate access visit, and a trip to the Melbourne Show, Bill told his 14-year-old son he was going to take him for an allergy test.

The test was in reality a DNA parentage test, to establish the likelihood of Bill being the boy’s biological father. The fallout is set to force the Federal Government to amend the Family Law Act so that men who prove they are not the biological fathers can recover child maintenance payments.

The case of Bill, whose identity is confidential, which went before the Chief Federal Magistrate, Diana Bryant, last year, has revealed that the court has no jurisdiction to order repayments to “biological strangers” in the same position as this man. The legislative gap applies to married couples who separated, and had child maintenance orders for children born before 1989.

Since then, the Child Support (Assessment) Act allows courts to order repayments where a presumed parent is later found not to be the biological parent. In the case of Bill, Ms Bryant said his only recourse was civil action to recover the $28,700 he had paid in child maintenance since 1987. Under the Family Law Act she only had power regarding “biological parents, step-parents, adoptive parents … parents as a result of artificial conception procedures … the applicant is, effectively, a biological ‘stranger’ [to the boy]”.

Geoffrey Greene, the federal director of the Shared Parenting Council of Australia, said more of these cases would emerge with the widespread access to DNA testing. “It’s awfully late in the day to be finding this out,” he said. “It needs to be fixed. You can’t start treating families different because of the legislation they fall under.”

Robert Benjamin, chairman of the family law committee with the NSW Law Society, said: “It clearly needs a change to the law because the only option you then have left is an action for deceit at common law – but you have to show active deceit, and deceit may well be difficult to prove.”

In a precedent last year in Victoria, Liam Magill successfully sued his ex-wife for $70,000 in damages and economic loss after DNA testing proved she had deceived him by telling him her lovers’ children were his own.

After the Herald brought Bill’s case to government attention, a spokeswoman for the Attorney-General said the need for amendment was being considered by the department, pending consultation with the child support agency.

The Australian Law Reform Commission this week completed its report on safeguarding human genetic material. The commission’s chairman, Professor David Weisbrot, said privacy, consent, quality assurance and counselling had been issues in parentage testing. While the Family Court documented 103 parentage testing orders in 2000-01, many more were taking place in other courts, and others were occurring either by consent, or without, outside the legal system.

Judging from the inquiry’s public meetings and submission, he did not see a nexus between the requirement to pay child support and the use of DNA tests.

“I don’t think most people want to prove that the child isn’t theirs,” he said. “They are not doing it to get out of payments, generally speaking … I don’t think it’s anything to do with the child – it is still the continuing anger with the other partner.”

The commission proposes there be no DNA testing without the consent of all involved, with a court order necessary if one party refuses.