NZ Election 2020: Grant Robertson casts National as chaotic in TV ad as Jacinda Ardern kills off prospect of wealth tax

"I won't allow it to happen as Prime Minister" - with those words Jacinda Ardern has completely killed off the prospect of a wealth tax under Labour. 

The Labour leader was campaigning in Christchurch on Wednesday, where she was caught in a rolling maul as she met with supporters in Riccarton Mall. 

Ardern firmly put her foot down speaking to the media as the prospect of a wealth tax was brought up again. 

"I won't allow it to happen as Prime Minister," she said, going to extreme lengths because even after repeatedly squashing it, the Greens won't let it go. 

"No other country has this form of taxation," Ardern told reporters. "Now is not the time to be experimenting with tax policy."

It came after Green MP Chlöe Swarbrick told Magic Talks' Ryan Bridge the Greens are discussing walking away from coalition negotiations over it.

"Actually, it's really disingenuous for Labour to try and say that they're ruling anything like this out, because ultimately it's the voters who will decide," Swarbrick said. 

Bridge asked Swarbrick if she had discussed refusing to support Labour in coalition or confidence and supply. 

"There are ongoing discussions all the time," she said. 

Her leaders walked it back on Wednesday. 

"There's no reason to think we wouldn't be supporting a Government in the coming years," said Green Party co-leader James Shaw. 

Not that Ardern really cares what Swarbrick has to say. 

"I'm not going to get into whatever discussions are being had by backbench MPs," she said. 

But she does care about attacks by National leader Judith Collins. 

"We are not going along with the concept of a wealth tax," Collins told a crowd of supporters in Hamilton. 

Having ruled it out multiple times, Ardern seems increasingly frustrated with National's tax attacks, calling it "desperate".

Collins doesn't think her attacks are getting desperate. 

"No, I think they're very real," she laughed. 

"Unfortunately a desperate tactic in the closing days of the campaign," Ardern described the attacks. 

"Oh, she shouldn't go into name-calling," Collins said. 

Labour's finance spokesperson Grant Robertson has gone further in a new TV ad. 

"If you're someone who values stability and consistency in these uncertain times, and maybe you've backed John Key or Bill English before, this is a message for you," Robertson says. 

"There's too much at stake right now to vote for National. They're unstable, they've had three leaders in three months, 19 resignations, a string of different positions on the border, and they've published a budget full of mistakes."

He's casting National as chaotic and reminding voters of the way this Government has handled crisis. 

"Now is not the time to put our recovery at risk."

Ardern as the crisis Prime Minister came back for a moment on Wednesday as the imam of the Al Noor mosque was targeted during her mall walkabout. 

Someone offensively yelled, "This is New Zealand, my country."

Ardern pulled him close and said "let's keep walking, my friend". 

Sometimes the campaign trail can take an ugly turn.