Green MP James Shaw has thrown his hat in the ring for the co-leadership role, Shaw chose to announce his running at Wellington's iconic bucket fountain.

Wellington-based MP James Shaw has confirmed he will contest the Green Party's co-leadership.

Shaw brought the announcement forward after Stuff.co.nz revealed his bid on Thursday.

He is the fourth candidate to make a pitch.

Stuff LEADERSHIP EYED: James Shaw.

First out of the blocks was MP Kevin Hague, followed by Gareth Hughes, who is also Wellington-based. Aucklander Vernon Tava is the only out-of-Parliament aspirant.

Shaw said the party needed "new energy". It was disappointed after falling well short of a 15 per cent target in last September's general election.

"The co-leaders are the most visible face of the Greens and need to appeal to a wide range of people," he said.

"We need co-leaders that can win those people over, who can overcome the fears of the 28 per cent of voters who considered voting Green in 2014 but did not."

A first-term MP, Shaw initially said it was "highly unlikely" that he would run.

Addressing his inexperience in Parliament, he said: "Achieving a bigger, stronger and more effective Green Party is not about years in Parliament and yelling contests in the debating chamber. It's about a proven record in connecting with people, telling them our story and translating that into votes, and that is something I do."

Shaw, 41, a former management consultant, said he was likely to be working with "experienced and effective" Metiria Turei, who was standing again for the female co-leadership.

He pointed to his track record in the Wellington Central electorate, although he has twice lost that to Labour's Grant Robertson.

"I took the Greens from 20.62 per cent to 29.58 per cent across two elections, turning the Greens into the second-largest party in the electorate," he said.

Across the country, Shaw won the highest percentage of party vote for a Greens candidate at September's election.

Shaw, the party's economic development spokesman, said market forces could help solve sustainability problems, but he would have to win over those suspicious of his business background.

Party delegates will vote at the annual conference in May, when co-leader Russel Norman steps down.