Conservative lobby group Family First is expected to present a petition containing more than 72,000 signatures to a select committee hearing submissions on legalising gay marriage today.
The select committee is considering 20,000 submissions on Labour MP Louisa Wall's Marriage (Definition of Marriage) Amendment Bill, which would legalise gay marriage in New Zealand.
Family First said in a statement its petition opposing the bill was signed by people from around New Zealand from "all walks of life".
The petition says: "I support the definition of marriage in New Zealand being maintained as one man one woman. I oppose any attempt to redefine it."
Family First national director Bob McCoskrie said the petition had exceeded similar campaigns in the UK and Australia per head of population.
"This is an incredible response considering it's not part of a formal referendum, and it certainly shows the level of public opposition to the bill. And the signatures continue to come in," he said.
"Our aim is to gain 100,000 signatures and to encourage politicians not to pass the bill."
The select committee, which is sitting in Auckland, is also expected to hear from the NZ Christian Network and NZ Campaign for Marriage Equality today.