Labour continues to apply the acid over National's economic plan, calling on leader Judith Collins to explain the full extent of the mistakes.
It believes there could be up to $8 billion worth of errors in the party's plan, released just over a week ago.
Labour hasn't released its own yet, but leader Jacinda Ardern says they will put out some "supplementary information" to follow September's Treasury update.
"What I will say is: ours stacks up; what I'm deeply concerned about is that the National Party's has a significant hole - you cannot promote tax cuts, as well as spending, as well as debt reduction and claim that you're not going to cut services," she told reporters in Auckland.
National has admitted to two errors, and adjusted the plan accordingly, totalling about $4 billion, but continues to deny a third, relating to transport funding.
It rejects the claim it double counted money by tagging $3.9bn to the non-existent NZ Upgrade Programme, as well as including it in the sum it's allocated to capital spending.
Ardern says she believes National has double counted: "Yes, it certainly appears to be the case. They've since made the claim that we'd see changes in the National Land Transport Fund; that still means an almost $4bn reduction right there".
"They have a lot of explaining to do, and I do expect as leader of the National Party that job should be up to Judith Collins."
Collins says there was "only one error, and the rest simply a different name for something, it's been explained by the economists".
"It's just a typical thing from the Labour Party finance spokesperson [Grant Robertson] the 'Minister of Misinformation'," says Collins.
She dismisses with a laugh Robertson's comment they should rip the plan up and start again - "he doesn't even have one".
But there have been a number of errors, counters Ardern, and "sizeable" ones.
"They represent $4bn - in just one case - worth of money that is now not available to them, they need to demonstrate what service cuts, what cuts in spending we'll see as a result," says Ardern.
She says the "high level of dismissiveness" from National about the errors is concerning.
"Our economic recovery will be critical for New Zealand, to say that $4bn doesn't matter, just is irresponsible."
Ardern wouldn't put a date on when Labour's plan would be announced, with barely three weeks to go until the election - and less than a week before early voting starts, but she says the September update laid out the bulk of its spending programme.
"PREFU obviously is in a sense giving that snapshot, it demonstrates what we as an incumbent government … very different to an opposition who has to demonstrate what their forward plan looks like; ours is there."