A cross-party attempt to reform New Zealand's abortion laws looked like it would emerge intact from a debate on proposed amendments until a dramatic last minute mistake axed one of its key provisions.

The amendments, known as Supplementary Order Papers or SOPs, were the subject of a lengthy debate that stretched from Tuesday afternoon to the early hours of Wednesday morning.

An attempt by ACT leader David Seymour to axe "safe areas" failed, but a last minute mistake by MPs supporting safe areas meant that safe areas were effectively nixed anyway, despite a definition for safe areas remaining in the bill.

Seymour proposed an amendment to remove safe areas from the bill. The bill initially allowed a safe areas to be established up to 150 metres around a place offering abortion services. It would be illegal to protest against abortions in these areas.

The intention was to prevent American-style protests where people getting abortions are harassed and intimidated before visiting clinics.

Seymour was concerned that the safe areas violated wider principles of free speech.

He described anti-abortion protests as "absolutely grotesque" but said the principle of free speech needed to be protected, "I've never defended anyone that I like when it comes to free speech, and that's the test of free speech, you've got to protect people that you don't like".

The first part of the amendment failed, but by a very tight margin, 59 votes to 56, however later in the night a second part to his amendment passed effectively by accident.

The second part of Seymour's amendment was to delete parts of the bill that would give effect to the safe areas. It went to a voice vote, where MPs vote by saying "aye" and "no", which it passed.

MPs then had an opportunity to call a conscience vote on the amendment as they had done for other amendments that night, but supporters of safe areas failed to do this, meaning the amendment passed. A late attempt by Green MP Jan Logie to save the provision failed.

This means that while safe areas remain in the legislation, the parts of the bill relating to establishing safe areas and making them function have been removed - effectively making it impossible to set one up.

Ross Giblin ACT MP David Seymour managed to have one of his key amendments pass.

Green co-leader Marama Davidson tried to prop-up safe areas by tightening their definition, depoliticising the process of their establishment, and halving the penalty for people caught violating the safe area from $1000 to $500.

National's Nikki Kaye shocked the house saying she would be supporting Davidson's amendment and voting against Seymour's.

"There will be women who will be intimidated, who will be harassed," she said.

Monique Ford Abortion debate parliament. Jan Logie Green Party MP

"I cannot support David's bill because I do not have confidence in the bullying and intimidation laws in New Zealand," she said.

In the end, Davidson's amendment also failed.

Logie submitted several SOPs, some promising to dramatically change the legislation. The most contentious would change the gendered language of the bill, removing references to pregnant women and replacing them with references to pregnant people, reflecting the fact that transgender men are capable of becoming pregnant. This will be voted on last.

Logie tried to effect this change during the select committee stage of the bill, but could not get consensus of the committee.

Two amendments, put up by Labour's Ruth Dyson and Louisa Wall attempted to tackle one of the more contentious aspects of the bill, which is its protection of the rights of people to conscientiously object to providing emergency contraception even in cases of rape.

Terry Bellamak, the President of the Abortion Law Reform Association of New Zealand or ALRANZ has been critical of that particular provision as it could prohibit people from accessing emergency contraception which is most effective immediately after unprotected sex.

"You can take emergency contraception up to 72 hours after unprotected sex but it's most effective in first 12 hours," she said.

Wall's amendment would require health practitioners to supply contraception, removing conscientious objection rights in those cases, but the vote failed to pass.

Dyson's amendment was narrower. It will require all DHBs ensure everyone within their catchment be able to access emergency contraception within 48 hours of it being requested. It managed to pass.

Darroch Ball of NZ First proposed putting the law to a referendum, this vote was broken off for a second round of voting which will occur later.

National MPs Melissa Lee and Parmjeet Parmar both put up amendments hoping to tighten the law to avoid abortions in the case of sex selection.

Parmar's amendment would reduce the period where abortions could be obtained without a statutory test to 12 weeks, because sex is more difficult to determine in that period. The amendment failed by a large margin.

It would also force health practitioners to refuse ultrasound scanning in situations where they have reason to believe that the purpose of the scan would be to obtain an abortion for the purpose of sex selection.

Lee's amendment would allow people to be sentenced to serve up to 7 years in prison if they provided an abortion on the basis of sex selection or disability. It is also part of a different section of SOPs and will be voted on later.

There were 36 amendments proposed in total.

The bill currently in committee stage, where individual amendments are debated by MPs. It is expected to come up for its third and final reading in the coming weeks, after which it will become law.

It's likely to pass third reading, having sailed through it's second reading last week 81 votes to 39.