Jacinda Ardern performed 'near-miracle' to win election - Helen Clark

Former New Zealand Prime Minister Helen Clark says Labour leader Jacinda Ardern has performed a "near-miracle" by guiding her party to victory in the 2017 election.

Ms Clark, the last Labour leader to guide the party to an election victory back in 2005, said taking the party from the depths they were in under Andrew Little to an eventual win was "incredible".

"I think Jacinda Ardern and the negotiators have done a superb job in bringing together New Zealand First and the Greens," she told Newshub.

"I'm pleased for the Greens - I think it's the first time they've had a real shot at this. I'm pleased for Labour and I'm pleased for New Zealand First.

"I really hope that together, they can make a difference on the issues that were being highlighted through the campaign as badly needing attention."

Ms Clark said National's call to "cut out the middle man" and vote for them instead of New Zealand First clearly worked against them when they went into post-election negotiations.

"Jacinda going into the negotiations not having bagged people she was likely to have to work with turned out to be the best strategy," she said.

"I was in the category of those who didn't really dare to hope... but I think Jacinda's shown incredible resilience.

"She picked herself up [after the election], she got into those negotiations and she's clearly been able to build a relationship with Winston Peters."

Ms Clark said she didn't believe Mr Peters would try to push Ms Ardern around on account of her relative inexperience, and believes they probably share a lot of common goals.

"I think that actually a lot of the socio-economic approaches are not that different," she said.

"They will readily agree that housing issues have got to be fixed, that mental health issues have got to be fixed... so I don't think you're going to see disagreement over those things."

Ms Clark says "the glue that holds coalitions together" is communication, rather than agreeing on everything - and promised New Zealand First would be loyal allies if they were treated right.

"When Winston Peters and New Zealand First gave you their word, their word was their bond. We did not have any difficulty in the running of our Government [with them on board]," she said.

And Ms Clark doesn't doubt whether Ms Ardern is up to the task of leading the country, given the huge positive change she's made since stepping up as leader of the Labour Party.

"In the two-and-a-half months since she's been the Labour leader, she's performed a near-miracle. She took the party from what was looking like a catastrophic defeat into Government," Ms Clark said.

"If that's not learning very, very fast on the job, I don't know what is."