Gay marriage could soon gain the protection of New Zealand laws as the country's Parliament voted this week in favour of the same-sex union bill authored by opposition Labor MP Louisa Wall.

Ms Wall's proposed legislation attracted 80 nods from her fellow NZ lawmakers with 40 rejecting the Labor initiative, according to a report on Wednesday by the Australian Associated Press (AAP).

The overwhelming support for the bill was sufficient to push the measure for a second round of vote and likely a third one before Ms Wall, who is openly gay, would see the realisation of her life advocacy.

Under the bill, gay marriage will be accorded the same legal rights bestowed by the NZ government to heterosexual unions, including the lawful adoption of a child.

The proposed Labor law will actually extend the existing protection accessed by gay couples in the country, local media reports said.

Analyst said the likelihood of the measure passing through three rounds of vote by the Parliament is quite big considering that latest NZ surveys pointed to close to 70 per cent of Kiwis supportive of the bill.

Another plus is the positive commitment from the country's conservative prime minister, John Key, who had earlier declared that he's "not personally opposed to the idea," of gay couples being married.

Mr Key voiced out his position on the matter shortly after U.S. President Barack Obama made known his personal backing for same-sex marriage, prompting analysts to conclude that the New Zealand PM was buoyed by Mr Obama's take on the controversial issue.

Ms Wall conceded that the Obama declaration played a big role on how the gay marriage debate is unfolding so far in New Zealand, saying "the timing was right," for the legislation.

"I think the catalyst was around Obama's announcement, and then obviously our prime minister came out very early in support," the Labor MP told the AAP.

She also credited the NZ Labor leadership for throwing it support to her proposed bill, the main aim of which, Ms Wall added, is "fundamentally about living in a fair and just society."

NZ conservatives, however, will come out in full force to strongly oppose the other reality being espoused by the proposed laws, according to Family First founder Bob McCoskrie.

Mr McCoskrie said exiting civil laws in the country should afford sufficient legal entitlements to gay couples, insisting that the provisions contained in Ms Wall's proposed legislation were pushing the envelope too far.

"Marriage has always been about the relationship of a man and a woman because of their natural potential to have children," the leader of the NZ conservative lobby group told AAP.

In neighbouring Australia, legislators are still locked on debates about the same measures though both the ruling and opposition party were equally opposed to the idea of legalising same-sex unions.

Labor Prime Minister Julia Gillard, however, has allowed her party members to vote on such bills using their conscience while Coalition leader Tony Abbott vowed to punish Liberal members who will cross party line on the matter.