Prime Minister Jacinda Ardern has again been forced to defend herself, and her ministers, from attacks from her Deputy Prime Minister, Winston Peters.

In a speech this morning, Peters – also the leader of New Zealand First – took aim at Labour, his coalition partner, and the Greens.

A Government of those two parties in a coalition, Peters said, 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, going off-script.

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

But Greens co-leader James Shaw has fired back: "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."

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

"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 along 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 this 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."

But, speaking to reporters, 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.