Government lawyers are due back in court this month defending flawed abortion laws against an effort to make them even worse.

The anti-abortion group Right to Life began its latest legal battle over abortion five years ago and the case has now reached the Court of Appeal. Last year, the group was buoyed when Justice Forrest Miller ruled in the High Court that there was "reason to doubt the lawfulness" of many abortions in New Zealand.

Indeed, Justice Miller went on to say, the Abortion Supervisory Committee itself "has stated that the law is being used more liberally than Parliament intended".

To which the only sensible answer is: thank goodness. Thank goodness the clinics and doctors and women of this country have managed to adapt such an outdated, cumbersome law so as to give New Zealanders access to the kind of reproductive health care one might expect of a modern Western nation.

But the problem is not just that time has passed this legislation by. Its flaws were clear the moment Parliament voted it into the statute books in December 1977, after an all-night debate during which more than a quarter of the House spent crucial hours either absent or asleep.

Mike Minogue, then National MP for Hamilton West, said at one point he was sick of arguing complicated issues to "certain sleeping gentlemen" who woke when the division bells rang and followed Bill Birch into the appropriate lobby. Only four of Parliament's 87 MPs were women, and all opposed the legislation.

Prime Minister Rob Muldoon, an outspoken abortion opponent, wasn't caught napping, but he went missing for eight hours. He complained later about amendments excluding fetal abnormality and rape as grounds for abortion, admitting he couldn't remember whether or not he'd voted on them. It turned out he hadn't. The law that passed that day had to be amended in six months just to get out of the starting gate.

But more important than the debating chamber slumber were the legislation's intellectual - or more accurately, anti-intellectual - roots: The Royal Commission on Contraception, Sterilisation and Abortion.

This poorly argued and remarkably conservative document continues to cast a long shadow, both through the laws it generated and because it is still being used as a guide for their interpretation. Justice Miller made that clear last year when he cited the royal commission in his ruling on the Right to Life case.

Under the current laws, a woman seeking an abortion in New Zealand must get approval from two certifying consultants on one of four main grounds. The cries of illegality from anti-abortion groups arise over the fact that more than 98 per cent of the abortions performed each year are granted on grounds of risk to the mental health of the mother.