Conservative Party leader Colin Craig says he is opposed to marriage between same-sex couples but he would support a referendum on the issue.

The Conservatives are yet to win representation in parliament but they are polling higher than some of the government's current coalition partners.

A One News poll conducted by Colmar Brunton has found that 63 per cent of New Zealanders think same-sex couples should be able to marry, while 31 per cent are opposed. Civil unions between same-sex couples have been allowed in New Zealand since 2005.

Mr Craig told TV One's Q+A programme on Sunday that he would support a referendum on the issue.

"If all New Zealanders decide `hey yeah we're ready for a change', fair enough, but I don't think that's where New Zealanders are at," he said.

Prime Minister John Key has said he is not personally opposed to same-sex marriages but the issue is not a priority for the government.

Labour MP Louisa Wall has drafted a bill to allow same-sex marriages and Greens MP Kevin Hague says he will put his Marriage (Equality) Amendment Bill into the next members' bill ballot where it competes with other bills for selection.

"The only difference here is the word marriage," Mr Craig said.