Prime Minister Bill English and Labour leader Jacinda Ardern speak to media after the second leaders debate in South Auckland.

The second leaders debate was as fiery as it was funny as Bill English and Jacinda Ardern went head-to-head over housing, balancing the books, poverty and much more.

Both leaders took it up a gear from their first debate last week and had endless zingers and political one-liners. They agreed if they had to take a policy from the other side it would be free GP visits for community services cardholders - both parties recently announced that policy within days of each other.

English committed on Monday night in the Newshub leaders debate that National would implement a target of getting 100,000 kids out of poverty if they're back in government.

NEWSHUB Prime Minister and Leader of the National Party Bill English and Leader of the Labour Party Jacinda Ardern speak during the debate.

Ardern said her entire reason for being in politics was to rid the country of child poverty.

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The debate kick-started with a question around trust and whether it's possible to be in politics and not lie.

While English said "none of us are perfect", Ardern was very frank about having never lied in politics but if she did she would own up to it and be transparent.

Both leaders were at times bolshie and very confident, Ardern warmed up faster than English but when he got on the same page it became a job for moderator, Newshub political editor Patrick Gower, to keep them under control.

From the issue of trust and credibility the debate shifted to policy, and once they'd both agreed on more free doctor visits, English used the opportunity to tell Ardern she should be taking up National's social investment policy.

NEWSHUB "I got up again," Bill English said of his career.

"Bill, it's called early intervention and Labour was built on it," Ardern fired back.

Housing was a contentious issue and Ardern got in one of her better lines of the night - "You've had nine years, it's time you handed over".

But English bit back at Labour's KiwiBuild policy and how they would be able to build homes if they planned to cut immigration.

NEWSHUB Ardern said during the debate that her entire reason for being in politics was to rid the country of child poverty.

Ardern pointed out they'd allowed for 5000 KiwiBuild visas to ensure they had the construction workers but that some of them would be New Zealanders.

"So New Zealand builders will get a visa to work in New Zealand?" was the response from English.

On whether the leaders wanted the price of housing to drop, English said he wanted prices to "stay flat while incomes rise" whereas Ardern said it was all about having "affordable housing".

Asked how he was different now to when he failed to win in 2002 as the National Party leader, English shot back, "I got up again".

The leaders got into a scrap over the government's plans for tax cuts next year and English delivered one of the worst received lines of the night that he'd spend his tax cut on meeting the costs of his six kids.

English wouldn't rule out re-entry to the Pike River mine but was cut off by Gower and the ad break before he had the chance to fully explain why.

On potential kingmaker, NZ First leader Winston Peters, both leaders agreed they wouldn't give him a shared prime minister job or a finance role.

Would either of them quit if they didn't win the prime ministership? No.

Who would they give a knighthood to? Ardern says former prime minister Helen Clark but she knows she wouldn't take it.

English says he's already working up a list and you're not meant to reveal who is on it until New Year's Day.

As to what they'd march in the street for, English said the right to govern while Ardern had the better received line of "ending homelessness".

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