More than 90 per cent of Kiwis who made submissions on the euthanasia bill want the proposed law change scrapped.

But backers of the controversial bill say scientific surveys are a better guide on public opinion and have consistently found majority support for euthanasia or assisted dying.

The Care Alliance analysed virtually all of the more than 38,000 submissions made to Parliament's justice select committee on Act leader David Seymour's End of Life Choice Bill.

It found that 90.2 per cent opposed the bill, 8.1 per cent were in favour and 1.7 per cent were neutral or unclear.

Most submissions were unique, and not form or postcard submissions. Twelve per cent were longer than a page and 90.5 per cent did not use religious arguments.

The bill would legalise voluntary euthanasia, giving people with a terminal illness or a grievous and irremediable medical condition the option of requesting assisted dying.

A private member's bill, it was drawn from the parliamentary ballot in 2017, two months before the health select committee reported to the House on its inquiry into the public's views on euthanasia, a report that contained no recommendations.

The inquiry was prompted by a petition following the death from brain cancer of Wellington lawyer Lecretia Seales, 42, in June 2015 shortly after she heard of the failure of her High Court bid to allow her doctor to help her die without criminal prosecution.

The Care Alliance's members include the Catholic bishops' bioethics centre, the Salvation Army, Lutherans for Life, Hospice NZ and the Christian Medical Fellowship.

Alliance secretary Peter Thirkell said the number of submissions to the justice committee and the proportion against euthanasia were significantly greater than in the health committee's inquiry.

Six of the eight health committee members voted against Seymour's bill at the first reading, having "listened carefully to the evidence, and voted accordingly".

"We hope the members of the justice select committee will demonstrate a similar respect for the mountain of evidence showing that legalising euthanasia is unnecessary, unwise and dangerous."

But Seymour said the justice committee submissions did not reflect public opinion in the way that a scientific survey did.

"Nobody would take seriously an opinion survey where the respondents were self-selected.

"What we have here is fewer than 1 per cent of New Zealanders who have made submissions. The overwhelming majority of them are less than a paragraph and they have done it in response to concerted campaigns by certain organisations."

Seales' widower Matt Vickers said the alliance had analysed the submissions thoroughly but scientific polls of New Zealanders, which had consistently shown 65 to 75 per cent support, were a more accurate depiction of society's views.

"I would expect that the committee will modify the bill to address the very valid and heartfelt concerns raised by submitters, ensuring that End of Life Choice is only made available to those who truly need it," he told the Herald on Sunday.

"I myself support very tight criteria and with this in place most concerns raised will be addressed."

He expected that with the committee's changes, the bill was likely to pass.

The last time Parliament considered assisted-dying legislation, the Death With Dignity Bill in 2003, it was defeated on its first reading, by 60 votes to 58.

An earlier Death With Dignity Bill was voted down at its first reading, 61-29, in 1995.