Former Green Party co-leader Russel Norman will resign as an MP and from the Green Party to head Greenpeace New Zealand.
Dr Norman, who stepped down from the co-leader position in May and was replaced by James Shaw, will leave Parliament next month.
In November he will become Greenpeace New Zealand's executive director, taking over from Bunny McDiarmid, who has been in the role for 10 years.
Dr Norman said he would also resign from the Green Party.
"Greenpeace's staunch position on political independence is one I have always had huge respect for and it is for this reason that I will [resign].
"I'd like to acknowledge the superb job that Bunny McDiarmid has done as head of Greenpeace over the last decade. And I'd like all of Greenpeace's supporters to know that, as your new executive director, I'll do everything I can to continue that tradition of great leadership."
Stephanie Mills, chair of Greenpeace NZ's board, said Dr Norman's optimism and vision, but also "commitment to civil disobedience and direct action" as a core part of democracy were reasons for his appointment.
In June, four Greenpeace protesters scaled Parliament's roof to call for greater action on climate change.
Dr Norman's resignation will see Marama Davidson become the party's 14th MP.
Ms Davidson, from Manurewa, Auckland, is a political commentator who has worked at the Human Rights Commission for ten years.
Green Party Co-leader Metiria Turei paid tribute to Dr Norman, saying there were few words to express how grateful the party was to him for his work.
"Since becoming co-leader outside Parliament in 2006 after the tragic death of Rod Donald, Russel has established himself as one of the most effective MPs in the opposition," Ms Turei said.
Dr Norman was a "constant thorn" in the Government's side and a passionate advocate for the environment and the disadvantaged, she said.
"With every close there is a new opening, and we are incredibly excited about Marama Davidson becoming an MP," Ms Turei said.
"Marama is a modern, progressive voice for Maori political aspiration and will also be a very welcome fourth member of the party's Maori caucus."
Dr Norman, 48, leaves politics having helped to double the Greens' share of the party vote to 11 per cent.
During that time, the Greens have not only become more a mainstream party, but the Green economics they have preached has become more commonplace.
Meanwhile, Tim Barnett, who has been the Labour Party's general secretary for three years and oversaw last year's election campaign, has announced his resignation.
In a statement, Labour Party president Nigel Haworth said Mr Barnett had accepted a new job, and applications for his replacement would open shortly.
In May, Labour leader Andrew Little distanced the party from a submission on the 2014 election, written by Mr Barnett and submitted to the Justice and Electoral Select Committee.
The submission said making enrolment to vote a pre-condition to receipt of various forms of state support, such as tax credits or Working for Families, should be examined.