Former Green Party co-leader Jeanette Fitzsimons honoured at memorial service in Wellington

A memorial service is being held in Wellington for Jeanette Fitzsimons, the former Green Party co-leader.

She died suddenly in March at the age of 75.

The service at Wellington Cathedral of St Paul includes speeches from former Green Party co-leader Metiria Turei, former Australian Greens leader Bob Brown, Green Party MP Gareth Hughes and former Parliamentary Commissioner for the Environment Dr. Morgan Williams.

After the first MMP election in 1996, Fitzsimons entered Parliament as a list MP for the Alliance but it wasn't long before strains appeared in the grouping.

She felt herself left out of its decision-making and the Green Party itself was increasingly unhappy with the Alliance's direction.

Fitzsimons won the Coromandel seat for the Greens in 1999, the country's first elected Green MP, and was disappointed when she lost it in the following election, although the party remained in Parliament due to its party vote.

She and her co-leader Rod Donald were strong influences in the change in public perception of the party as a group of sandal-wearing tree-huggers.

Fitzsimons suffered a stroke in hospital on March 5, where she had been taken that morning after falling while working on their farm, husband Harry Parke said.

In March, Prime Minister Jacinda Ardern said Fitzsimons had been a steward for the New Zealand environmental political movement. During her 14 years in parliament, Fitzsimons was an early voice for action on issues now considered mainstream, like climate change, clean energy and the deteriorating state of New Zealand's water, Ardern said.

Greens co-leader James Shaw said Fitzsimons had immense generosity and humility, and understood that you must work with those you disagree with to forge a consensus. Fitzsimons was never about personality politics and was driven by what was the right thing to do, he said. "She treated everyone with respect no matter their politics, and she treated everybody with dignity."