The 61-year-old appeared in her element for the night, pinning the Labour leader down on tax and housing, all while debating confidently and energetically.

"I felt very good ... I thought I did well. I enjoyed it and I could have gone on tonight," she said.

Ms Collins walked the fine line between interjecting and hectoring Ms Ardern, at times straying towards patronising the prime minister, 21 years her junior.

As Ms Ardern called out the opposition's lack of climate change plans, Ms Collins responded with "What for, dear?".

The National party leader denied settling out deliberately to unsettle the prime minister, who retains a healthy polling lead.

"You don't just get a long monologue in a debate. You're going to have some to and fro. It's called debating," she said.

Lobbyist and former National staffer Matthew Hooton praised Ms Collins, saying her performance "was the best we have seen by any leader for decades ... probably only rivalled by David Lange in 1984".

However, Ms Collins earned the only boo of the evening in an odd moment defending Donald Trump.

"He has actually done some quite recent stuff with Israel and UAE. That's better than war, don't you think? He hasn't been ready to rush into war," she said.

In August, the two countries signed a peace deal, though the countries have never been at war, with UAE agreeing to diplomatically recognise Israel.

"It is a worry when the best thing you can say is at least we haven't had war," Ms Ardern countered.

Ms Collins blundered when speaking to journalists after the debate, asserting the Middle East was enjoying peace.

"I was trying to think of something positive to say because I think that the Middle East not being in war is quite a good thing," she said.

In fact, there are numerous conflicts in the Middle East, not least a US-backed Saudi Arabian intervention in a Yemeni civil conflict that has cost tens of thousands of lives, and violent long-running conflicts in Iraq and Syria.

New Zealand's Defence Force has a presence in Egypt, Jordan, and Lebanon, and training forces in Iraq and Afghanistan.

Still, Ms Collins' naivety on foreign affairs didn't stop her from winning the backing of the majority of pundits, who delighted in her entertaining witticisms.

Asked about Ms Ardern's infamous cover shot with Vogue, Ms Collins said she wished it was her.

"Absolutely would I like to be there, there's no problem with that. Any political leader who says they wouldn't is a liar!" she laughed.

And on the fate of deputy prime minister Winston Peters, whose New Zealand First party has slumped in the polls, Ms Collins said he was "irrelevant" and wouldn't be re-elected.

"As a Christian I do believe in miracles but I tell you what, he won't be one of them," she said.

Australian Associated Press