New Zealand's parliament has passed a bill decriminalising abortion and allowing women to choose a termination up to 20 weeks into a pregnancy.

Voting to remove the procedure from the country's Crimes Act changes a law that has been in force since 1977.

Previously, two doctors were required to approve an abortion - and this could only happen if there was a "serious danger" to the pregnant woman's health.

The bill passed on its third reading by 68 votes to 51.

An earlier plan to put the issue to a public referendum was abandoned during the proceedings.

"From now abortions will be rightly treated as a health issue," Justice Minister Andrew Little said in a statement following the vote on Wednesday.

"The previous law required a woman seeking an abortion to go through many hoops," he said, adding: "The changes agreed to by parliament will better ensure women get advice and treatment in a more timely way."

For more than 40 years, abortion was the only medical procedure considered a crime in New Zealand - unless it was performed under exceptional circumstances.

The legislative vote in parliament was labelled a "conscience issue", meaning that MPs did not have to vote along party lines.

The reform bill, issued by Jacinda Ardern's government, means that a woman no longer has to be assessed by a health practitioner for mental or physical wellbeing before 20 weeks.

Women would be able to refer themselves to an abortion service provider and would have to be made aware of counselling services.