Prime Minister John Key says Jeanette Fitzsimons' contribution to politics in New Zealand has been significant and will leave an important legacy.

The Green MP today announced she will retire after 13 years in Parliament.

"Jeanette has been the cornerstone of the Green Party and her hard work and expertise will be missed.

"Her passion for the environment, coupled with her warm and engaging nature was a fearsome combination.

"She has been a trailblazer in New Zealand politics but never let the political process distract her from her core values.

"This is a rare and commendable attribute.

"Jeanette will be missed. Not just by those sharing her political views, but by all members of Parliament who have been touched by her hard work, humanity and humility.

"I wish her well in her retirement. She has done much to deserve it."