The Labour and Green Party leaders have made a joint appearance at a massive FIRST union rally, with almost 1000 people attending.

Greens leader James Shaw told the crowd he was there as the "warm up act" for "our next prime minister".

"It's an act I hope to repeat many times in our government that starts this Saturday," he said.

Shaw said the election had been a white-knuckle ride, but the party was focused on its three policy areas - water, environment and poverty.

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He spoke of how the party wanted to head towards a carbon neutral future - but that wouldn't mean job losses. Workers on oil rigs would be needed in the geothermal sector, for example.

"All of those skills are directly transferable."

In comparison, the National Party did not have a plan to deal with coming change, and risked people losing tens of thousands of jobs, he said.

His ideas on work brought polite clapping. When he mentioned ending poverty, however, the crowd roared.

Shaw pledged to return the social safety net - the welfare system - to a level where people were not in poverty.

The loudest noise of all was reserved for Labour leader Jacinda Ardern.

She described her beginnings working at a supermarket, giving a special shout out to Countdown employees.

"We have always been a party of working people," she said, describing workers as Labour's "heart". "In many ways I feel this election is an election where we are getting back to basics."

She said everyone needed a job, something to do, and Labour wanted to ensure that happened. She pledged to lift wages to $16.50 minimum, gaining another huge cheer.

Ardern said it was a risk to let the "drift" under National continue, and urged the workers to "choose change".

Organisers counted 923 people present, plus media.