Pensioners are holding out in a dwindling minority opposing gay marriage - as 2013 looks possibly to be the year for it to become reality.

A Herald-DigiPoll survey into same-sex marriages found a stark generational divide: 60 per cent of respondents older than 65 said marriage should remain only between a man and a woman. But 70 per cent of people under 40 said the law should be changed to allow same-sex marriages.

Labour MP Louisa Wall, who is behind the bill to legalise gay marriage, said studies out of universities had found even stronger support among young people, above 80 per cent.

"For older people, homosexuality was foreign; it meant things like mental illnesses. It was illegal. People could go to jail - so, of course, they can't relate to it.


"Older New Zealanders wouldn't have seen two same-sex people who love each other."

Homosexuality was criminal until 1986.

"The reality for them growing up is they've only seen relationships [between a man and a woman]," Ms Wall said.

But the generational divide was really between grandparents and grandchildren.

"It's their grandchildren's generation who, in polls, say they're the most supportive.

"If [older New Zealanders] have grandchildren who are gay, or exploring expressions [of sexuality], you'll want to have the opportunity to celebrate with them. For your grandchildren to have the option to marry will be a wonderful thing."

Ms Wall said the 37 per cent of older people who supported gay marriage might well have been influenced by their grandchildren.

But Family First national director Bob McCroskie said there were other divides, too - men were more opposed than women, and there were differences between rural and urban constituents.

"It simply shows it's an issue that's polarised New Zealand."

Such an issue should not be decided by 120 MPs, but rather put to a public referendum, Mr McCroskie said. If there was an open debate on the underlying issues - particularly with an emphasis on the fact civil unions had been legislated - he was confident marriage could be left as it is.

Gay marriage would become an increasingly contested fight through 2013 and the Government should not be rushing through the process to avoid it becoming an election issue in 2014, he said.

New Zealand's Marriage Equality Bill passed its first reading this year by 80 votes to 40 and sent to a select committee for study.

The major issue so far has been from churches seeking a legal clause to let ministers refuse to marry same-sex couples, an apparent conflict between discrimination and freedom of religion.

The committee will report to Parliament on February 28, with a second reading scheduled for March 20. A third and final reading could happen in May.

Overall, 59 per cent of survey respondents backed gay marriage and 38 per cent were against - compared to 54 and 41 per cent in June. The poll interviewed 500 people in the second week of December, and has a margin of error of 4.4 per cent.