Euthanasia eligibility changes made in David Seymour's End of Life Choice Bill

David Seymour's proposed euthanasia legislation is one step closer to becoming law.

Wednesday saw the End of Life Choice Bill debated by the Committee of the Whole House in Parliament, which is where individual MPs can present amendments to the legislation for debate and vote.

The Bill will stay in this crucial stage for weeks as each part is examined. Despite the longest select committee process in Parliamentary history, including more than 35,000 submissions, no major changes were made.

That makes the Committee of the Whole House stage crucial for the controversial legislation which needs several amendments to gain support from the Green Party, New Zealand First and other MPs in the third reading.

Wednesday evening's main vote related to an amendment made by Seymour that narrowed the eligibility of someone seeking euthanasia to only individuals with a terminal illness that will likely kill them within six months.

That passed with a conscience vote by MPs 74 votes to 44.

Originally, the Bill said adults with a terminal illness or a "grievous and irremediable" medical condition could be eligible for euthanasia. 

But taking out the "grievous and irremediable" clause was necessary to gain the Greens' support. Seymour has signalled he believed the original clause was sufficient but was willing to change it to get the Bill across the line.

Other amendments will be proposed throughout the committee as politicians examine each part.

There was vocal opposition to the Bill in the House on Wednesday, including from National MPs David Carter and Maggie Barry, concerned about issues of coercion and the age of eligibility amongst others.

The Bill passed in its second reading 70 votes to 50, but even if it passes its third reading, it will likely still need to be approved by the public.

New Zealand First's support is contingent upon a referendum happening. An amendment securing that will be voted upon at a later stage.

But Seymour has said that it is possible for the Bill to pass without a referendum included.

"I've kept my word. [Peters] has kept his. If we work together and if other MPs also support the referendum idea, I think the Bill can pass relatively easy. If there is not a referendum added to the Bill in this committee stage, I think we can still get through all the way, but it will be a lot harder," he told The AM Show on Wednesday.

"It's a pity there is the extra complication, but if that is how we can actually deliver choice for those New Zealanders who want it and it is the overwhelming majority of New Zealanders, then I think it is a good deal".

A Newshub-Reid Research poll last year found support from 71 percent of respondents, while 19.5 percent didn't approve.