The move to legalise gay marriage in New Zealand is a step closer after it passed the select committee process.

Parliament's government administration select committee has sent The Marriage (Definition of Marriage) Amendment Bill for its second reading.

Sponsor of the bill, Labour MP Louisa Wall, says it's a big step for the supporters of same-sex marriage.

"This is another important milestone towards achieving a fairer more equal New Zealand," she said on Wednesday.

"Marriage equality is about fairness and choice. This process has showed that message has really resonated with New Zealanders and has been echoed overseas with the recent passage of similar legislation in the UK," she said.

But lobby group Family First says the fact there were 21,533 submissions shows it's an issue that divides the country.

It accused political parties of trying to ram the bill through.

"It is a major change to an important human institution and foundation of our society, and in a healthy democracy, the people are entitled to speak and deserve to be heard in full. It should not be rushed, and democracy should not be denied," said national director Bob McCoskrie.

"This is a cynical attempt to ram through a highly controversial law change without due consideration."

The select committee recommends an amendment to the bill to protect the religious beliefs of celebrants and organisations.

The second reading of the bill will be on March 13.

AAP smm/nb/lhh