A bill allowing a debate on same-sex marriage had double the chance of being drawn after Green Party MP Kevin Hague also had a private member's bill in the ballot to legalise same-sex marriage.
Mr Hague said "the time had come" for gay marriage in New Zealand.
"One of the things we said was regardless of which bill got drawn, we'd both be putting our full weight behind them. I am very pleased to say I will be campaigning hard out to support Louisa's bill."
He said it was likely the bill would have majority support at the first reading, because Prime Minister John Key has indicated he would support the bill in its early stages.
"I think John Key's support is quite important because within the National Party caucus that is effectively the green light for people who support the bill to be able to vote for it," he said.
JOHN KEY'S VIEWS ON GAY MARRIAGE
Prime Minister John Key said last month he would support a bill to legalise same-sex marriage at its initial stage, but would not guarantee his support would continue through to the final reading that would see it become law.
Mr Key has previously said he votes on conscience issues according to the views of his Helensville constituents - he told the NZ Herald in 2008 that he was "more liberal than my voting record".
He said the Government itself would not put up a bill for same-sex marriage.
"It's not my number one issue, that's for sure. That has been true of most of those conscience or moral issues. The previous Government had a lot of those on the agenda from prostitution law reform through to civil unions. We haven't had any and that's reflected that these are tough economic times and we need to spend our precious time in Parliament resolving those issues."
He said he recognised it was an issue "for a small group of New Zealanders" but it was not a big issue for the Government.
In the past, Mr Key voted against a bill that would have defined marriage as between a man and a woman. He also voted against civil unions. In 2003 he voted in favour of the Prostitution Reform Bill at its first reading, but voted against it at the third reading.
DAVID SHEARER'S VIEWS ON GAY MARRIAGE
Labour Party leader David Shearer said the party would cast conscience votes.
"We've always gone for a conscience vote on these issues - and that's what the caucus decided it wanted to do," said Mr Shearer.
"We haven't asked which way our members will go."
Mr Shearer said he would support marriage equality.
"I think it's the reality of our times - it effectively puts in place what's already in existence."
"All New Zealanders will have the opportunity to have a say through the select committee process - so I think it's important that the bill comes forward."
HONE HARAWIRA'S VIEWS ON GAY MARRIAGE
Mana leader Hone Harawira this afternoon said he would support the bill through its first reading in Parliament.
Harawira had come under pressure from his party to back gay marriage despite previously expressing discomfort about it, saying he was "morally very conservative".
Last year, when asked about the issue at Otago University, he did not answer directly but said: "I'm not a great fan of a society of huge choice, to tell you the truth".
However, today he said Mana believed in equal rights. He would back the bill to select committee stage.
