The second reading of a bill to legalise same-sex marriage is likely to be held in Parliament this evening.
The controversial Marriage (Definition of Marriage) Amendment Bill passed its first reading in August with 80 votes for and 40 against, but MP Louisa Wall says she is "sure" its support will slip at its second reading.
Conservative Party leader Colin Craig said on Sunday that public support for Wall's bill is slipping.
He told TV ONE's Q and A programme that public support is shifting in the direction of traditional marriage.
"Public support is moving not because people want to deny anybody anything, but we recognise we already made that provision.
"This is a rushed process. New Zealanders were denied the right to speak," he said.
In response, Wall argued that it is a "standard process" and still hopes she will get enough votes from MPs to pass the bill through its second reading.
"From the Prime Minister to the leaders of both the ACT Party, United Future, Mana, Maori Party and obviously there's a strong group within Labour and the Greens, so I'm very hopeful." she said.