Green MP Kennedy Graham has said goodbye to Parliament, telling his colleagues that he was leaving with "no hard feelings".

Graham said in his valedictory speech that he did not want to revisit the circumstances of his resignation last week, when he quit in protest at former co-leader Metiria Turei's actions.

But he said today that he was prepared for "whatever fate was in store" when he spoke out against Turei alongside colleague David Clendon.

And he stood by their ultimatum to the party over Turei, despite angry criticism from the party that the two MPs had undermined the Greens at a critical time.

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"If politics transgresses conscience, politics must cede," he said. "This is the decision we took, simple as that."

Graham joined the Green Party in 2005 after 34 years abroad, including a stint at the United Nations, and became an MP in 2008.

The climate change and foreign affairs spokesman said today that his career had focused on the two existential threats faced by humanity - climate change and nuclear weapons.

He cited several highlights, including a role in the NZ delegation which negotiated the South Pacific nuclear-free zone in the 1980s. He also referred to the cross-party group on climate change he formed at Parliament, which produced a plan earlier this year for New Zealand to reach zero net carbon emissions by 2050.

This sort of cross-party work was an example of the "best kind of politics that Parliament can display", he said, and he hoped the Vivid work would continue after his departure.

Graham spoke about the importance of tolerance in politics, saying he had most admired other MPs who had showed respect and courtesy "across the traditional lines of division".

Remaining open to the views of others was "arguably the most critical thing we can display" as global events became more tumultuous, he said.

The Green MP became emotional when speaking about his six grandchildren, saying they "had a way of lighting up our lives and pushing us to be more aspirational".

"I've done my best here for them, as I know we all aspire to do for future generations."

Six of the other 13 Green MPs attended Graham's farewell speech, including leader James Shaw, who gave him a long hug afterwards.