Seymour was joined by Green leader James Shaw, National's Nikki Kaye and Chris Bishop, and Labour's Iain Lees-Galloway as well as End of Life Choice's Dr Jack Havill and Matt Vickers, the husband of Lecretia Seales who unsuccessfully took the issue to the High Court after she was diagnosed with a non-operable brain tumour and died in 2015.
Vickers said Seales would have been delighted to see the legislation arrive at Parliament and urged MPs to support it.
"Obviously when she took the court case her ultimate goal was to get legislative change and this is the mechanism by which that happens. So she'd be very happy to see that this was going ahead."
While most parties are allowing MPs to lodge conscience votes, NZ First leader Winston Peters said his MPs would vote for it at first reading but further
support would be conditional on a referendum on the issue.
He said the public should decide – not 120 MPs. That will mean MPs such as Shane Jones – who does not support euthanasia – will support it at least in the beginning.
Ardern said she would support the bill provided it contained safeguards to protect the vulnerable because she believed people should have choice.
However, National leader Bill English – a Catholic – said he did not support euthanasia and believed Seymour's bill lacked the necessary safeguards.
National MP Maggie Barry was also strongly opposed, saying it was a "licence to kill".
"It would make us the most liberal country in the world to die."
Labour's David Clark was yet to decide but was concerned it would be a "slippery slope", referring to his grandmother who suffered from manic depression and had tried to take her own life.
"I have several concerns – one is broadly about society as a whole and its ability to ensure community is put before the needs of individuals and the way in which we can risk a slippery slope with euthanasia. My own grandmother attempted suicide a number of times when I was a child because she felt that she was a burden on society."
Pacific Peoples' Minister Aupito William Sio said he would vote against it. He listened to the arguments at a select committee inquiry last year but had not heard anything to change his mind. Members of the Pacific community had spoken to him about it and while some were not worried about it "for many Maori and Pasifika life is something that is very sacred."
End of Life Choice President Maryan Street urged MPs to at least let the bill go to select committee for submissions.
"We want people to have the confidence they have the choice to die well, not badly, at the end of a terminal illness or when they can no longer bear their irremediable condition. We want them to have a choice."
Labour MP Phil Twyford said he would vote against it and did not support euthanasia.
"I think that doctor-assisted suicide and doctor-assisted euthanasia put vulnerable people in our communities in a terrible situation. I just don't support it."
National's Nikki Kaye said for her it was a matter of compassion and she believed it was time New Zealanders had a say on the issue so it should go to select committee. However, it was important to be respectful of others' views and other MPs might oppose it on ethical or religious grounds.
New National MP Simeon Brown was opposed, while Labour's Greg O'Connor was in favour of individual choice on the issue.
