The Green Party's longest serving MP is retiring at the next election, and says the Government has not been "transformational".

Gareth Hughes, 38, is retiring after a decade in politics to get some years in with his two children before they grow up.

MONIQUE FORD / STUFF Green Party MP Gareth Hughes in his office at Parliament's Bowen House. He is retiring after a decade in politics.

Hughes' children are nine and 12: old enough to realise that their dad often leaves for work before they get up and returns after they get home, or is constantly on his phone when he is there. His mother died earlier this year, causing him step back and think.

"If I do another term, my eldest will be 16 and he won't really want to hang out with me anyway," Hughes laughs as he exclusively shares his plans with Stuff.

Hughes is going out proud, and firmly believes the Green Party will return to Parliament at the election, as well as Government. Over his one term in Government he was a key figure pushing for the ban on new oil and gas exploration, and in opposition he won a ban on shark finning.

MONIQUE FORD / STUFF Gareth Hughes is going out proud, and firmly believes the Green Party will return to Parliament at the election. He says the Government has not been "transformational."

But he's also frustrated. Frustrated that the pace of change has not matched what he sees as the problems facing the country and globe - climate change and rising inequality.

"Across my 10 years here, things have actually got worse. Emissions have increased, we are still losing a hundred million tons of topsoil every year - our most precious resource - homelessness is growing," Hughes says.

"I don't think the Government has been transformational. There's been pockets of transformation, but you know, I don't think historians are gonna look back at it and say 'This was a turning point on the scale of the 1930s or 1980s'. And I think that's desperately needed."

"It's a disappointment that we aren't seeing the change I think we need. As a father, I'm desperately worried about the future of the world."

Hughes says New Zealand needs a change on the scale of those revolutions - the first Labour Government creating the welfare state and the fourth one tearing it apart.

"As I reflect across 20 years of activism I realise that I've spent 20 years winning campaigns, but each one's kind of like chopping off the head of the hydra. There's always another equally important campaign right behind it. I've spent 20 years fighting the symptoms, not the source."

"I've grown up knowing nothing but the revolution of the early 1980s. This is this operating system which was uploaded in New Zealand and people have tried to install better policies or better programs, but if they don't work with the system, they are crashing."

MAARTEN HOLL/STUFF With Green Party co-leader James Shaw. Hughes ran unsuccessfully for the party's leadership.

Hughes thinks it is key that the Greens push the country towards a new economic system able to properly fight climate change, and it isn't yet.

"Our ambitions have to match the scale of the emergency. We have to build a movement because if we are going to see the transformational change to save the planet from literally burning we have to do more than just sort of exhaustedly crossed the line at 5.01 per cent. We have to keep growing and growing and have strong ambitions."

The Government's main climate change law, the recently-passed Zero Carbon Act, is "scaffolding" - Hughes says. But the rubber hasn't really hit the road yet, and he's extremely disappointed that existing oil and gas permits are being extended.

ROSS GIBLIN/STUFF Promoting a petition to scrap the private sale of fireworks.

His criticisms of the party match many made by its committed and extreme left-progressive membership base. A member-completed review of the Budget Responsibility Rules, which limit government spending and debt significantly, suggests the Greens scrap them.

Hughes says he was against the rules from the start when they were first suggested to make the Greens more electable ahead of the 2017 election. But lost the caucus battle to resist them - to a man he had lost to before, current co-leader James Shaw.

Shaw beat Hughes in the 2015 co-leadership race, but Hughes says there was no tension following this.

AMBER-LEIGH WOOLF/STUFF Hughes with fellow Green MPs accepting a petition at Parliament

"It wasn't much of a hit. I mean I thought Kevin [Hague, the presumed front-runner] was a total shoo-in and I was actually standing to show my commitment to the Greens and actually throw out some ideas," Hughes says.

His low-point from his time in Parliament is the same low-point of many Green MPs: The 2017 campaign, when co-leader Meteria Turei resigned after admitting to benefit fraud and two senior MPs resigned in protest of her actions.

"There was a horror week in the campaign where I think we had two or three emergency conference calls, which was each a disaster worse than the last," Hughes says.

"I was doorknocking in Gisborne by myself. Not a single person said they were gonna vote Green. It was in the rain. I crashed my car, dropping my kids off at school. That was the sort of horror period."

That campaign resulted in the Greens' lowest result in over a decade, but also its first term in Government. Yet despite his experience as the longest-serving MP Hughes did not become a minister.

"I put my name forward and it would have been great and you know, had the Greens had more roles that could have been a possibility," Hughes says.

But he isn't keen to focus on the missed opportunities. Hughes will remain a force in the party, as many other former MPs do, and is looking forward to supporting his wife in her career for a while, after a year of "world-schooling" his kids around the globe. Getting to Parliament itself was a bit of a shock, let alone for a decade.

"I was just a working class kid from Gisborne who cared about girls and cars and rugby more than politics that somehow fell into a passion for environmentalism, somehow got to Parliament. So I've always pinched myself, the fact that I'm here."