The freedom from seeking re-election has allowed departing MPs of all political stripes, to speak their minds in their valedictory speeches.

Contributions have been breath-taking, heart-wrenching and laugh-out-loud hilarious.

Former immigration and workplace relations minister Iain Lees-Galloway made a shock return to parliament to admit his sacking by PM Ardern was deserved, taking ownership of his shortcomings with refreshing honesty.

On his way out the exit door, he also suggested means-testing superannuation, and rolling health services within the country's no-fault accident scheme, the ACC: two reforms that would take mighty political courage.

Ruth Dyson, a Labour lioness of 27 years service, agreed with Mr Lees-Galloway and asked Ms Ardern to individualise welfare benefits - a cause the PM has steadfastly opposed despite a report telling her to do so.

Departing National deputy Nikki Kaye recounted the phone conversation where she told prime minister Sir John Key she had breast cancer, wit him replying "you're not f****** going anywhere".

Clare Curran revealed she was suicidal during her ousting as communications minister, saying she feared an MP would take their own life due to the pressure of a "sick" political system and media as "needing to turn the mirror on itself".

She targeted Radio NZ, the state broadcaster she tried to merge with TVNZ, as having "lost its way".

David Carter, a conservative former agriculture minister urged Ms Ardern to fix the country's emissions trading scheme and rebuild parliament.

Jian Yang used his statement to refute "conspiracy stories" of disputed loyalty to New Zealand after three terms dogged by allegations he, a former spy-trainer in China, was a communist party plant.

But the show-stopping contribution came from Sarah Dowie, a two-term National MP from the southernmost city of Invercargill.

Ms Dowie was re-endorsed for a third term and would have been a minister should the Nationals have triumphed on September 19.

Instead, she's giving politics away after the revelation of an affair with ex-National MP Jami-Lee Ross, describing herself as "New Zealand's scarlet woman".

"When I started my parliamentary career I would have done anything to make it to the caucus room. The drive was immeasurable," she said.

"On leaving I have the same level of intensity. I could claw at the windows or walk across hot coals to get out."

Ms Dowie described the psychological pain she felt after being "manipulated" by her "predator" former lover, who faces a growing tally of claims of abuse from other women.

Mr Ross also faces criminal trial next year as part of a donations scandal and has left National to run for a conspiracy theory-backing fringe party.

Ms Dowie has faced no suggestion of wrongdoing outside the relationship, yet it is her political career that is over.

She believes it's because women face white-hot media scrutiny that men don't.

"I'm not shying away from the fact the affair was wrong," she told AAP.

"We all know in Australia and New Zealand, politicians have affairs. Its not great behaviour but we're human.

"But why was my private life so interesting as opposed to anybody else's?

"He was this predator, who was manipulating me and manipulating the media ... it was a series of hit jobs and at no point did the media stop and reflect."

Ms Dowie said she decided to use her speech to outline the abuse and call out media as she wants a cultural shift on how women are treated - and says it's already happening.

Since her valedictory last week, Ms Dowie has been flooded with messages of support.

"My phone has been blowing up left, right and centre. People have been reaching out from Australia," she said.

"Women are coming forward with relationships that they're in. They now recognise the patterns.

"They're seeking advice about how to get out of relationships or deal with it.

"And I hope New Zealand is ready to have this conversation about these forms of abuse."

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Australian Associated Press