Labour finance spokesperson Grant Robertson is slamming National's Christopher Luxon and Nicola Willis over what he says are "rubble" claims of a "rock solid" tax cuts plan.
Luxon and Willis are under mounting pressure after independent economists claimed there was a $500 million yearly gap in National's proposed foreign buyers' levy, which would contribute to the party's tax relief package.
"You can be assured this is a far more responsible approach than Labour who are already spending up so much in this campaign that they've had to book it against lots of future budgets," Willis told AM on Friday, again disagreeing with the economists' fiscal hole claims.
"Our tax plan is rock solid," said Luxon on Thursday.
But Robertson has rejected the National leaders' claims as "turning to rubble".
"Nicola Willis and Christopher Luxon's economic credibility is shot," Robertson said on Friday.
"They are constantly saying they are 'rock solid' in their costings but none of it adds up - their rock-solid rhetoric is turning to rubble."
But National has rejected accusations of the plan not adding up, with Willis saying the economists claiming a fiscal hole had "underestimated how much demand there will be for homes from foreign buyers".
But the economists - CoreLogic head of research Nick Goodall, former Reserve Bank analyst Michael Reddell and ex-New Zealand Initiative research fellow Sam Warburton - maintained there's a massive hole in the plan.
"The bottom line was you just get nowhere near their numbers on any plausible assumptions," Reddell said.
And Robertson said National needed to "front up and be honest with New Zealanders about their policies".
"The $2 billion hole in National's costings is the equivalent of paying for about 3800 senior nurses, 4000 teachers or 2700 police every year."
Robertson also called a prospective National/ACT/New Zealand First Coalition a "slash and burn Government". He referred to ACT leader David Seymour's promise to scrap 15,000 public service jobs if elected.
A recent Newshub-Reid Research poll - taken before the alleged fiscal hole was discovered - found most voters - found 51 percent thought now was the right time for income tax cuts versus 36.1 percent who didn't think it was.
