Labour's two Coalition partners are officially at war, with NZ First saying the Greens are "away with the fairies" and the Greens hitting back today, saying NZ First are "an agent of chaos".

The veneer of Coalition collaboration has been stripped bare with less than nine weeks to the election and as both parties fight for their survival.

NZ First leader Winston Peters says the Greens are "away with the fairies" and Greens co-leader James Shaw hit back this morning.

"We've known for a long time, that the closer we got to election, the more likely it was that NZ First would start misbehaving," Shaw told Newstalk ZB's Mike Hosking today. "We have just taken it in our stride really."

Labour had not been able to exercise any discipline over NZ First over the past three years, Shaw said.

"If you look at some of the difficulties that the Government has had over the last three years, a lot of them have come down to NZ First ankle-tapping them and blaming them for saying they can't get anything done.

"I know they like to say they are a force for moderation; it's more like an agent of chaos."

Peters yesterday took a swing at Labour, his coalition partner, and the Greens, warning that if the two parties were to join in a Coalition it would be a "nightmare".

"If you think a red-green [Labour-Greens] government is good for you, then you're in cloud cuckoo land," he said yesterday, going off-script.

"These people are away with the fairies," he said, referencing the Greens and their wealth tax policy.

Shaw told reporters: "In my experience over the last three years, NZ First has not been a moderating force, but a force for chaos."

He added: "Their organisational culture is chaotic."

Shaw told Hosking this morning that NZ First could have expressed its opposition to policies and issues - such as the rebate for electric vehicles - much earlier, saving public servants' time and taxpayer money. "They basically killed it off at the last minute after the public service wasted two years of effort. That's a familiar pattern."

He did not think NZ First would be back in Parliament, based on current numbers, but the Greens would work with them again "if that's what it takes".

Peters said the Greens and Labour in power together without NZ First as an "insurance policy" would mean more tax for New Zealanders.

"They say they want to get close to you: they're right. [It's] so they can put their hand down the side of your body, and into your wallet."

But perhaps his most cutting blow was reserved for his Cabinet colleagues.

"I've been in this game a long time, and I've never had three years so difficult," Peters, who was first elected to Parliament in the late-1970s, said.

He added it was difficult to "manage circumstances when you're surrounded by plain inexperience".

Speaking to reporters outside the House yesterday afternoon, Peters doubled down on these comments.

Asked why a Labour-Greens government would be a nightmare, Peters said: "Because experience matters".

"I knew when we made the decision in 2017 that I was going into a Cabinet with a whole lot of people with no experience at all."

Prime Minister Jacinda Ardern was again forced to defend herself, and her ministers, from attacks from her Deputy Prime Minister.

Speaking to reporters yesterday, Ardern said her Deputy Prime Minister's comments were not fair.

Asked about the nightmare comments, Ardern said: "I think the Government that we have been over the last three years has been one focused on New Zealanders".

She said she put Peters comments down to "an election period".

"It's an election period and you will see parties starting to differentiate."

At his party's annual conference this weekend, Peters said that NZ First had "used common sense to hold Labour and the Greens to account. We've opposed woke pixie dust".

He took aim at the fact that a number of Government Ministers from Labour have been forced to resign their positions over the last three years.

He said while front-bench Ministers have been "spilling out of Cabinet" they have never been any questions about "competency or controversy" when it came to his party.