National MP Dr Nick Smith has lodged a member's bill to establish a Kermadec Ocean Sanctuary which could pass into law with the support of the Green Party, if the bill is drawn from the ballot.
But the Nelson MP insists his motivations are conservation, not to drive a wedge among Government support partners over the issue.
NZ First has opposed a sanctuary that curtails Maori fishing rights, but the Greens have said that environmental values outweighed fishing interests.
Smith's bill would ban mining and fishing in the sanctuary and, if drawn, could pass with the support or even just the abstention of the Greens.
A sanctuary was the subject of a Green Party member's bill and a Government bill under the previous Government, but it was put on ice to try to resolve objections and a legal challenge by Te Ohu Kaimoana, the Maori Fisheries Commission.
A solution to a sanctuary issue is included in Labour-NZ First agreement as well as the Labour-Greens one, but this morning NZ First MP Shane Jones said the parties were no closer to a solution.
"I haven't spoken to [the Greens] formally, but I think it's fair to say our friends in the Green Party, they're aware of the NZ First position," Jones told TVNZ's Q+A programme.
"It's a challenge for iwi themselves to come up with a pragmatic solution. But in the absence of a pragmatic solution that has us as NZ First agreeing to it, there will be no Kermadec Sanctuary."
Green co-leader James Shaw has previously said his party's support on a National MP's member's bill would depend on the nature of the bill.
Smith said he lodged his 40-page bill on Friday, and it was similar to the stalled Government bill. It would protect the 620,000sq km surrounding the Kermadec Islands in a "no mining, no fishing" sanctuary.
"I have indicated to the Greens National's intent to introduce a member's bill. With their eight votes and National's 56, there's a clear parliamentary majority for the sanctuary to proceed.
"They've always consistently supported the sanctuary and I'm confident of their support for this bill."
He rejected the idea that he was motivated by political mischief.
"I'm making quite plain that whether it is this member's bill, the existing Government bill, or a Green bill, National simply wants to see this sanctuary put in place.
"This would enable 15 per cent of New Zealand's exclusive economic zone to be in a protective area."
He said his bill included a joint-conservation board with iwi representation. Te Ohu Kaimoana would also be involved in a 25-year review that could see mining and fishing rights returned, if those resources had sufficiently recovered.
"But it would require legislative change," Smith said.
Because National has 56 MPs, it can use the members' bill process to get laws passed with support from either NZ First or the Green Party. It can also pass bills on its own if NZ First abstains - or with Act's David Seymour if the Green Party abstains.