Former Prime Minister Helen Clark says abortion should be removed from the Crimes Act, and should be a decision to be made between a woman and her doctor.
Earlier on Monday, leader of the opposition Simon Bridges said abortion should be "rare, safe and legal" but did not think it needed to be removed from the Crimes Act.
Ms Clark says that while the Act is "liberally interpreted", abortion law still needs a shake-up in New Zealand.
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"We have complicated law because the Crimes Act says abortion is an offence - but then we have the Contraception and Sterilisation Act, which gives grounds on which you can get an abortion: if you feel your life is threatened, or your physical and or mental health is threatened.
"In practice that is liberally interpreted, however Jacinda Ardern is right to say that the Crimes Act provision should be removed," Ms Clark said on The Project on Monday evening.
Ms Clark tried to liberalise abortion law while she was in Government, but there were roadblocks.
"I tried when I was Minister of Health, a long time ago, to get rid of the provision to have to ask two certifying consultants for permission," she said.
"I think that needs to go, so it is simply a matter of a decision made between a woman and her doctor.
"I received a lot of opposition from those who were receiving the income from being certifying consultants... it just ran into a lot of problems as a legislative amendment."
Speaking to RNZ on Monday, Mr Bridges said he put emphasis on abortions being "rare".
"I don't see the case for change," he said.
Justice Minister Andrew Little has asked the Law Commission to review and consider modernising New Zealand's abortion law, and any law change would go to conscience vote in Parliament.