Voluntary euthanasia legislation is "becoming normal around the world" ACT leader David Seymour says.
Nearly two-thirds of MPs last night voted in support of Mr Seymour's bill which would allow assisted dying.
Watch David Seymour speaking with Kim Hill on Morning Report:
The End Of Life Choice Bill would allow people with a terminal illness the option of assisted dying. At its first reading in Parliament last night 76 MPs voted in favour and 44 against, and the bill now goes to the justice select committee.
Mr Seymour said the fact that similar legislation was being adopted by many countries and states, including Canada and the Australian state of Victoria showed it was becoming normal.
"Because people can see it's possible to design a law that gives choice for those who want it and protection for those who want nothing to do with it."
Mr Seymour said much of the opposition came from a religious perspective.
"I do think it's curious that every single Member of Parliament who spoke last night against the bill is somebody who is known to have deeply held religious convictions. I respect that absolutely, but it's curious that not one of them mentioned it.
"I think the challenge for people who come from that perspective is that we all respect each other's spirituality, and each other's faith, but the quid pro quo on that is that you have to respect other people's choice.
National's Maggie Barry has called the bill a "license to kill" and warned it could leave the elderly vulnerable to abuse. National's leader Bill English told the House last night it would remove a principle at the core of the law - the blanket prohibition on taking the life of another.
Mr Seymour agreed to support an amendment for a referendum giving the public the final say, in return for the votes of New Zealand First's nine MPs.
He said it would have got to select committee even if New Zealand First had voted against it, but the nine votes was a more comfortable margin, and the prospect of a referendum might encourage some MPs towards the bill.
"It might well sway some Members of Parliament who are a little bit worried about what they're voting for to be able to say there's a final say from members of public."
An amendment for a referendum to be added to the bill would have to be passed by Parliament and that was not certain.
The provision also allowing people with a "grievous and irremediable" medical condition the option of requesting assisted dying did not include mental illness, he said. The person must be of sound mind, and understand assisted dying and the decision they were making.
"Someone with depression, for instance, by definition has a very warped view of the value of life and would be disqualified under that clause.
"And they would not have qualified in the first place because it is not a grievous, irremediable, irreversible medical condition."
The bill goes to the justice select committee which will begin hearings early next year.