Julie Anne Genter says she has the broad appeal to co-lead the Green Party to a greater share of the vote, promising to speak out against the Government where appropriate and improve links between the caucus and members to ensure the MPs are properly representing them.

Genter joins Marama Davidson in declaring her candidacy for the co-leadership.

Nominations close tomorrow and a nationwide campaign will take place over two months before a winner, as voted by party members, is announced on April 8.

"Under my co-leadership, it will be crystal clear to all that the Green Party is a force to be reckoned with, that we will not be pushed around or taken for granted by anyone."

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Genter said being a minister outside Cabinet was an advantage.

"There's nothing stopping me from judiciously critiquing the Labour-led Government where we have differences. In some ways, it's more powerful coming from a minister."

She said the survival of the party may be in question if it does not manage to carve out its own slice of political turf.

"It's vital for our survival in this term that we both can demonstrate that we're achieving real change and keeping our promises, and differentiate from the Labour-led Government to show where we can be more ambitious for people and for the environment."

She concedes she will be bound by collective responsibility in her portfolio areas of women, associate health and associate transport, "but I'm in charge of them, and we're getting good outcomes ... [and] the other co-leader could also potentially speak about issues that I couldn't."

Asked what she would change, she said the party could be better at communicating with and listening to its membership.

"I don't think we've done as good a job as we could at communicating why we're doing what we're doing, or demonstrating that we are listening to the membership.

"Around our deliberations and position on the Waka-Jumping Bill, I think we could have done a much better job at engaging with members who were raising concerns. We should have engaged earlier in a discussion about whether or not we should support it.

"We're going to have to be really deliberate in engaging with the party and making sure we're representing their views, because we're only here by virtue of the party. And we have to be really clear with the party membership about what the potential costs would be [if we don't support the bill]."

She said the co-leader needed to be able to speak on a broad range of topics while also ensuring each MPs' strengths were being used.

"I've been effective at communicating Green policy and values on a wide range of issues - women's rights, medicinal cannabis, mental health, and I've also demonstrated credibility in finance and economics and transport, and been the spokesperson on climate change."

Genter is often seen to represent the educated, bicycle-friendly urban liberal side of the party, but she said her appeal was wider than that.

"My track record and the communities I've actually engaged with show that I reached out a lot further. My political origin is very much one of activism, being passionate about peace issues, democracy, social justice, inequality and environmental issues. For me, they're inseparable."

She said she moved to Auckland so the party would have greater representation there, but "would quite happily live in Golden Bay".

Asked about her Maori credentials, she said she was "absolutely committed" to the Treaty of Waitangi, adding that she was the only Pakeha minister to do her swearing in in te reo.

"And if Marama is elected, I'll support her. She has a really important role to play in the party, whether or not she's co-leader. And I learn from her and our other Maori members all the time."

Genter, 38, was born in the US and became a New Zealand citizen seven years ago, though hasn't managed to completely shed her Californian accent.

Asked if that might count against her, she quipped: "We had an Australian co-leader before. Surely Americans are not as bad as Australians. I never really considered myself proud to be an American. I'm very proud to be a Kiwi.

"I will respect whatever decision the members make. I'm not standing because I think I'm the only person who thinks she can be co-leader. I'm standing because I think the party deserves to have a choice, and I think I have a lot of skills, solid experience and a proven track record."