More than 90 percent of public submissions oppose the euthanasia bill currently going through parliament.
The Care Alliance, which represents some groups opposed to euthanasia, analysed the nearly 38,000 submissions made to the Justice Select Committee on the End of Life Choice Bill.
Care Alliance Secretary Peter Thirkell said it was a record number of submissions for any bill, and more than 90 percent were opposed.
"These are heartfelt. This is a cross-section of all New Zealanders, and they are very well-informed submissions - these aren't just a few people with funny ideas," Dr Thirkell said.
He is calling on MPs not to dismiss the submissions, which include 2000 from medical professionals.
"I think it behoves the Justice Select Committee to treat them with the care, dignity, respect and gravity which is justified in the circumstances."
But the MP in charge of the bill, ACT leader David Seymour, said the submissions were not a representative sample of actual levels of support or opposition.
"I think opponents [to the bill] have done a very good job getting people to submit, perhaps believing that select committee submissions create a de-facto referendum on a piece of legislation," he said.
"However I would point people to consistent findings of reputable polling companies over 20 years which show in fact 70 percent of New Zealanders - that silent majority - do want choice and change in this area."
Mr Seymour said there are now 150 million people living in countries with legal, assisted dying.
"Over 20 years, not one jurisdiction that has legalised has gone back, and I think that really tells you something about public acceptance of the legislation once they see how it really works."
If the bill passes a second and third reading on a conscience vote in parliament, a public referendum is likely to be held.