Pressure is piling on National to release its costings and advice for its foreign buyer tax policy after revelations the party only got advice on one aspect after releasing the plan.
Newshub revealed on Sunday National only got advice from a tax expert on whether the policy could be in breach of tax treaties with other countries two days after the party released its policy.
"Clearly, National has been caught on the back foot and is scrambling to provide evidence it should have gathered before announcing its policy, which makes it look like the party gunning to be the Government has been blindsided by international laws," senior Newshub political reporter Amelia Wade said.
Part of National's tax policy, which was released last week, is to add a 15 percent levy on foreign buyers purchasing a home over $2 million, but there are concerns this could be a legislative breach.
For example, Article 24 of New Zealand's double taxation treaty with China - signed in 2019 - clearly states Aotearoa can't tax Chinese buyers more than Kiwis.
But National is confident it doesn't break international law and will "find a way" to get the policy across the line.
"We can find a way through, other equivalent places like Australia and Vancouver have these taxes - and all we're trying to do there is gain a bit of extra revenue to give some relief to the squeezed middle," National's Paul Goldsmith told AM last week.
But not everyone is convinced, with calls intensifying for National to release all its costings and advice.
"Revelations on Newshub tonight [Sunday] that National only got an expert to review their tax plan two days after it was released adds further fuel to the call for Christopher Luxon and Nicola Willis to release all costings and advice they have received on it," Labour finance spokesperson Grant Robertson said.
"That's a huge mistake and it appears they only sought advice in a panic after several experts made it clear their dodgy plan was likely a breach of our international agreements."
Robertson said this comes despite Willis telling Newstalk ZB on Thursday that "National had sought independent legal advice to check that we can do this while complying with our Free Trade Agreements and Tax Agreements".
But Robertson said those comments look like they came before the party engaged "with the expert", following the revelations by Newshub on Sunday.
"National is relying on bringing in nearly $3 billion dollars from foreign buyers to fund their tax cuts, but nearly every expert says those numbers simply aren't possible," Robertson said.
"If Christopher Luxon is so rock solid in his belief his numbers and advice are correct then he should have no opposition to releasing them."
Robertson said each day another aspect of National's tax policy "falls apart" and he believes voters deserve a chance to be able to examine "this house of cards before they vote on it".
"National just needs to get permission from SkyCity to release the work they did for them on the gambling part of their policy so it can be examined. Given it relies on an increase in gambling it's in the public interest to know," he said.
"If National's revenue streams don't add up their tax cuts are unaffordable. They will have to scrap them or make even deeper cuts to public services like health and education."