Jacinda Ardern has called it scaremongering but National has stepped-up its attacks on Labour over tax - releasing a new "let's tax this" campaign ad.

The ad lists the taxes National claims will be introduced under Labour - a capital gains tax, land tax, regional fuel tax, extra income taxes, a water tax and "fart tax".

Labour has accused National of scaremongering over tax, given it has not committed to a capital gains tax or land tax, and specifically ruled those out on the family home. Leader Jacinda Ardern has also ruled out increases to income taxes, but will scrap National's planned tax cuts in favour of its own families package.

Under Labour's climate change policy all sectors including farmers would pay for emissions, though farmers' costs would initially be offset.

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The 15-second National ad concludes: "there's only one way to stop Labour's taxes: party vote National".

Campaign chairman Steven Joyce said New Zealand's tax system was broad-based and fair, and there was no need to bring farmers into the ETS "when no other farmers worldwide are included".

"Labour needs to front up and be honest about its tax agenda. It's quite obvious they have one and they don't want to talk about it."

The Labour Party has promised a royalty on water if it is in Government, saying users in rural areas would pay around 2c per 1000 litres and the money would be given to councils and iwi to restore waterways. The charge would be set after consultation with industry and iwi.

Labour's policy in 2011 and 2014 to introduce a capital gains tax was replaced by former leader Andrew Little with the promise of a tax working group to look at the whole tax issue but to seek a mandate for any changes at the 2020 election.

Ardern has kept the tax working group but wants to implement changes without seeking a mandate - saying the housing crisis that has taken place under National means waiting until the next election to take action would be too long.

Labour has proposed a regional fuel tax in Auckland to help pay for improvements to the transport network, particularly in rail and including light rail to the airport.

New Zealand First leader Winston Peters has declared he will not support a Labour Government unless Ardern reveals what taxes will be introduced, and continued his criticism of Labour over its tax policy while campaigning in Whangamata today.