Prime Minister Jacinda Ardern says she'll be backing a Bill legalising assisted dying in order to let individuals make their own choices.
Act leader David Seymour's fiercely debate End of Life Choice Bill is expected to have its second reading in the House on Wednesday evening, with MPs voting individually based on their consciences, rather than by party lines.
Ahead of the vote, Ardern said while there would be a range of personal views within Labour, she would be backing the Bill, as she did during its first reading.
"It's been my view that while there are a range of strongly-held beliefs, and people have the right to hold those, I ultimately want people to make their own individual decisions," she told reporters.
"The best way I can do that is by enabling them to have that choice and by voting in favour."
Meanwhile, Labour's Willie Jackson – who says he will support the law through a second reading to allow for more debate - said the party's Māori caucus was split on the issue.
"There's a divided view in terms of the Māori caucus, it's splitting both ways," he said.
Former Māori Party co-leader and Associate Health Minister Dame Tariana Turia in March joined a campaign against Seymour's Bill, saying it was important maintain tikanga Māori in regard to death.
The Bill passed its first reading 76 votes to 44 and received a record 39,000 public submissions during a fraught Select Committee stage.
While Seymour has said he is confident it will make it through another round, opponents argue it'll go down to the wire.
"It's hard to tell. Some might make up their mind on the night in the chamber," National's Maggie Barry said on Tuesday.
If the Bill does make it through this week's vote, Barry has vowed to lodge more than a 100 amendments to the law, threatening to push a third and final debate well into next year.
But she denies it's a stalling tactic.
"It is not filibustering. There will be substantial issues," she said.
Seymour has promised if the Bill passes its second reading he'll remove a controversial clause allowing people suffering from a "grievous and irremediable medical condition" to request assisted dying, limiting it to those with a terminal illness likely to end their life within six months.
If there isn't time for the vote on Wednesday, the Bill will not return to the house until July 31.