ACT leader David Seymour has pleaded with his colleagues for a "speedy, efficient and civil" debate on euthanasia as MPs begin thrashing out the details of his legislation.
Watch MPs debate the bill LIVE:
The End of Life Choice Bill was before Parliament again tonight, with MPs in favour and against each armed with legislative changes aimed at winning over their colleagues.
The legislation passed its second reading 70 votes to 50 last month, but much of that support is conditional on major changes being secured.
The bill's architect, Act Party leader David Seymour, had at least 30 changes ready to go while one of its most vociferous opponents, National MP Maggie Barry, has more than 100 amendments.
Speaking in Parliament, he said his amendments should address most MPs' disquiet, meaning there was "not really a huge amount to be discussed".
"I hope that we can have a speedy, efficient and civil debate on this matter," Mr Seymour said.
Mr Seymour aimed to tighten the legislation to cover only those with a terminal illness - an amendment designed to appease the Greens and secure their vote.
New Zealand First's support depends on there being a public referendum - a move Mr Seymour also supports.
National MP Maggie Barry previously said she had 120 amendments lined up, but today confirmed it could easily go beyond that.
Before the debate tonight, she said it was not just filibustering.
"It is not filibustering. Filibustering is where you put in useless time-wasting things, this is reflecting the genuine concerns of the vulnerable,'' she said.
Ms Barry said it was not easy casting a conscience vote, and if MPs got it wrong their constituents would tell them so at the next election.
"We're lying awake at 2am worrying about unintended consequences and bad legislation, so we ultimately are elected to make up our minds. If our respective electorates don't agree with the stand we've taken no doubt they'll make that felt come election time," she said.
National MP Alfred Ngaro had also said putting it to a referendum would be irresponsible given how complex the issue is.
"If we struggle with the complexity of this issue here how are we going to be irresponsible to send out a question, which would only be one question, to the public to try and make a decision that could bring huge harm?"
"It's irresponsible to even think about a referendum on an issue like this," he said.
In Parliament, he said it was vital that the bill went through a "robust" process.
"This is not about filibustering. This is about as serious as it gets," Mr Ngaro said.
"A number of us are taking these calls, not only because we personally hear from people in our community, but because we know the importance of this bill and what it will set as a precedent in this country."
Mr Seymour disagreed a referendum would complicate things, and said putting it to public would actually strengthen the process.
"Normally MPs make law without any possibility of a citizens' veto, so we're actually giving the public extra choice and putting extra scrutiny on the bill," he said.
Mr Seymour said he continued to feel quietly confident MPs would line up with what he says is the overwhelming majority of New Zealanders who want choice.
"We're not counting any chickens, we're not popping any champagne corks or anything like that as some people have suggested. There's still a lot of work to do to make sure that MPs' position lines up with the position of the New Zealand public," he said.
National MP Simon O'Connor - a staunch euthanasia opponent - was one of a group of National MPs who vowed to put forward scores of amendments to try soften the legislation, which could prolong the debate for months.
He was quick to push back on the call for a quick process in the House tonight.
"I find that unfortunately attempting to gloss over already what is incredibly serious," Mr O'Connor said.
"We get this wrong and people innocently die."
Labour MP Poto Williams, who has previously supported the bill, commended Mr Seymour for his "courage" for raising the debate, calling it "perhaps the most visceral" question MPs would ever consider.
She challenged her colleagues to be honest with the public in their arguments.
"It's about accuracy of information, not misinformation. It is about debate, not conjecture," Ms Williams said.
National MP Lawrence Yule, who has previously voted for the bill, said his final decision would depend on the legislation's eventual shape.
"I am looking for solutions. I am not looking for this debate to be delayed for five months," Mr Yule said.
"We won't all agree and the vote will be tight, but I would hope that there is wisdom, decency and maturity in this House that we can get the best possible legislation".
Labour MP Louisa Wall told MPs she was sure the process would be a "constructive discussion".
"Everybody here has people that they love, that they have journeyed with through those final stages.
"I know for all of us this is a topic that we will debate and discuss in a very respectful way"
The debate will stretch until Parliament rises at 10pm on Wednesday evening. It will resume on 14 August.
Depending on how long MPs take to debate the hundreds of changes, the debate could continue into next year.
If debate at committee stage goes on too long there will come a point where a referendum at the 2020 election is no longer possible, because the Electoral Commission would not have enough time to prepare.
Mr Seymour said that point would be well into next year however, so there was still at least six months if not more to get it across the line.