ACT leader David Seymour's End of Life Choice Bill has passed its final reading in Parliament four years after it was first put in the ballot box.
The Bill - which will let terminally ill adults with less than six months left to live access assisted dying or 'euthanasia' - passed its final reading on Wednesday in a conscience vote, with 69 votes for it and 51 against.
But just because the legislation passed its final reading, it won't actually become law unless the public vote to pass it at the 2020 general election.
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That was a condition of New Zealand First, which offered its support for the Bill if it was put to a referendum. Kiwis will vote for it alongside a referendum on recreational cannabis.
MPs narrowly voted to put the Bill to a referendum last month, with 63 voting in favour and 57 against. New Zealanders will be asked: "Do you support the End of Life Choice Act 2017 coming into force?"
The Bill passed its first reading 76 to 44. It passed the second reading with a slimmer majority of 70 votes against 50.
The Bill then moved to the House where amendments were proposed. Anti-euthanasia MPs including National MP Maggie Barry - who has strongly opposed legalising euthanasia - put forward about 120 amendments.
"Unfortunately when it went through the select committee process, we had decided to leave the substantial stuff - the big debate - to the House," Barry told Newshub on Wednesday.
"But nothing was debated properly and not a single amendment went through."
The Bill has faced fierce opposition from faith-based organisations, to terminally ill patients and medical professionals. There are fears elderly people could be coerced by family pressure.
Seymour is confident that the Bill will keep people safe, despite a rally outside Parliament on Wednesday urging MPs not to pass the legislation.
"I would say those protesters, have nothing to fear," Seymour said, when asked about the rally outside.
He said there's "no question" some people are "scaremongering".
"But there are a lot of New Zealanders with legitimate concerns and I'd be more than happy to meet with people and answer them and I'll keep doing that over the next year if this Bill passes."
There has been support for the Bill. A Newshub poll last year found that 71 percent of New Zealanders were in favour of euthanasia.
In his speech to Parliament, Seymour paid tribute to Lecretia Seales, a pro-euthanasia campaigner who was denied the right to die in a 2015 High Court battle.
He pointed out a number of changes that have been made to the Bill to make it safer.
It previously allowed people with "grievous and irremediable" medical conditions to be eligible for assisted dying, but those terms were removed from it.
Barry said that didn't matter because "no one knew what it meant anyway".
The Bill also now only allows assisted dying when two doctors - one with five years' experience - decide if a person with a terminal illness and less than six months to live, should be eligible.
The doctors can also recommend that a psychiatrist evaluate the mental stability of the person.
No one can become eligible for assisted dying simply due to age, disability, or a purely psychological condition, and no written consent or advanced directive can substitute for a person demonstrating their eligibility.
Additionally, the Bill also includes protection for health professionals who have a conscientious objection to euthanasia.
Barry said she hoped the Bill wouldn't pass because she's not convinced it has sufficient safeguards.
"This is very serious and this Bill is not fit for purpose and won't protect the vulnerable... We will fight this through to the referendum."