James Shaw has announced he will be stepping down as Green Party co-leader in March.

"It has been the privilege of my lifetime to serve as New Zealand's Climate Change Minister for the last six years and as Green Party co-leader for nearly nine," Shaw said in a statement on Tuesday.

"I'm very proud of what the Green Party has achieved over the last eight years."

Shaw will be speaking from Parliament from 11am on Tuesday.

He said he would remain in Parliament to support his Members Bill, which would insert a new clause into the Bill of Rights Act stating that everyone has a right to a clean, healthy and sustainable environment. The bill was introduced to Parliament in December and is yet to have its first reading.

He said the Greens had become party of government, with ministers, for the first time and had made political history by increasing its support at the end of each of our two terms - "a feat no other government support partner had achieved".

It was especially gratifying that the Zero Carbon Act which pass with with unanimous support across Parliament had survived its first change of government, he said.