National has begun its fightback against the invigorated Labour Party with a new attack ad focusing on two new taxes announced by new leader Jacinda Ardern.

And National says it too is a winner from the 'Jacinda effect' with its supporters responding to an appeal for funds.

NationaI is taking aim at Labour's proposed water tax and regional fuel tax for Auckland, while saying its policy is to lower tax.

New Zealand First is also targeting Labour's yet-to-be-determined water tax, with leader Winston Peters saying voters were entitled to know how much the tax was before the election - and not after.

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National campaign chairman Steven Joyce says the Jacinda effect has jolted National as well as Labour.

"We've seen a big fundraising boost and a big boost in activity," he said.

"There was a sort of sense that the election campaign wasn't quite happening yet and then suddenly it's happening."

He sent out an email on Monday asking for donations and got back over $100,000 in 24 hours.

Joyce, who is also Finance Minister, said he was not surprised by the boost in support for Labour since Ardern took the leadership almost two weeks ago.

The Greens and New Zealand First have dropped as their soft vote has headed back to Labour.

National, seeking its fourth term in Government, is largely unchanged.

National in the past had focused on Labour, the Greens and New Zealand First, lumping them together. But Joyce said they would be focusing more on Labour and differentiating it with National.

"Things like water tax, regional fuel taxes, those sorts of things - I think the public are ready for a conversation on what the issues are and what the contrasting approaches are going to be for the next three years," said Joyce.

"I think that is where we will head in this campaign quite quickly."

National has produced a new digital attack ad on Twitter and Facebook suggesting Labour's slogan should be "Let's Tax This" instead of "Let's Do This."

"New leader, same party, @nzlabour have already announced plans for 2 new taxes that would hit hard-working Kiwis in their pocket - what next?"

Ardern has repeatedly refused to rule out lifting the top tax rate beyond its current level - 33c on income over $70,000.

Labour went into the 2014 election promising to introduce a new top tax rate of 36c on income over $150,000.

Joyce said that some of National's tactics might change but not the basics.

"We knew we had to run like hell to win this election campaign and we are going to have to run like hell to win this election campaign. That doesn't change."

He said Prime Minister Bill English would be demonstrating his passion on the campaign trail, for such policies as social investment.

"He has got a lot of strong attributes that a lot of people recognise.

"He is experienced. He has got a passion for New Zealand in terms of a lot of the outcomes for Kiwis. For him it is not just about the economy; it is what you do with it."

Peters has slammed Labour's water tax announced this week calling it ill-conceived and "a tax upon production and food."

The end users, hard-working Kiwi families, would ultimately pay the tax.

Ardern has said the amount of tax on water would be worked out after the election.

But Peters said: "This is an election campaign period and people are entitled to know what the tax is before they vote and not after."

He saw no valid comparison with own coalition policy - which is not to state a preference until after the election result is known - because his party caucus and council made a democratic decision about such matters.

Peters said he would not be changing his approach to the election in the wake of Ardern's leadership - "not in any way, shape or form."