Sustainable NZ leader Vernon Tava says he has no plans to do a deal with National over the Upper Harbour seat at this stage.

But the leader of the new blue-green party, which could be a coalition partner for National, isn't ruling it out a deal in the future.

Yesterday, National Party deputy leader Paula Bennett said she will not be standing again in the Upper Harbour seat so she could concentrate on her role as National's campaign chair for the 2020 election.

It has fuelled speculation about whether the safe National seat could be a launching pad for a new candidate - such as Chris Luxon - or used in an Epsom-like deal with a potential coalition partner.

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Tava said the focus for Sustainable NZ was on getting enough party votes to cross the 5 per cent threshold and enter Parliament.

But he would not rule out doing a deal with National in Upper Harbour, or any seat, if winning a seat would deliver a few Sustainable NZ MPs to Parliament, even if the party fell short of 5 per cent.

"Who knows? You would have to make the calculation though," Tava told the Herald.

"That might work, but what would that do for the party's future prospects? Perhaps it's better to maintain independence this time and keep an eye on the longer vision. These are the sorts of things you need to weigh up."

He stressed there had been no discussions with National about that prospect.

"It's not a 'oh yeah, definitely' or a fait accompli, and there's certainly been no discussion or pre-agreements with anybody.

"It's not a focus. It's not the plan. I can certainly say that."

New Zealand First leader Winston Peters took a swipe at Tava yesterday when he criticised National's appointment of Bennett to the campaign chair role.

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"This decision is so that the National Party can axe her prior to coalition negotiations in 2020, after they've realised that Vernon Tava and his planned [Sustainable NZ] Party is a headless chook, albeit being fed organics," Peters said.

Tava said he struggled to know what Peters meant.

"It's very quaint language, characteristically it's Winston. I thought maybe I'm a bit young to get the reference."

Asked if he was being fed organics, Tava said: "I don't think he has any special intelligence on this. I suppose it's a general go at anybody who talks about the environment. You're some sort of hippy, according to Winston."

Tava said he now had the 500 members required to register a political party with the Electoral Commission, and was yet to decide which electorate to stand in.

He lives in Auckland Central but grew up and works in the North Shore.

Asked about potential coalition partners, National Party leader Simon Bridges has said that he expected new parties, including in the blue-green or Christian-conservative space, to become more prominent in the lead up to the election.

He will announce next year whether National will be open to working with New Zealand First in 2020.

Tava said Sustainable NZ could get as much as 10 per cent of the party vote, and would be targeting centrist voters, not those who lean left and vote for the Greens.

"They vote on issues like the economy but also the environment - water, conservation, sustainable fisheries, saving native species.

"We can work with National. We can work with Labour. The last thing we would want to do is repeat the terrible mistake the Greens have made to only work with one side.

"Green voters are firmly on the left. They are last people we are expecting to attract."

Tava has previously stood for the Greens in Northcote in 2011, and unsuccessfully stood for the National Party candidacy in the Northcote byelection last year.