National leader Christopher Luxon is disputing criticism from Goldman Sachs that his promised tax cuts will increase the cost of living.
It comes as the Council of Trade Unions - a strong Labour ally - claims only 3000 households would actually benefit from the maximum tax cut National's offering.
The election campaign is rolling on for Labour without its leader.
Labour's Carmel Sepuloni was among those visiting Wellfed in Porirua on Wednesday to learn how to make good kai for cheap - a big focus of their campaign.
It's a big focus of National's campaign too. It said its tax plan will help up to $250 a fortnight.
To get that, the family must be spending at least $300 a fortnight on childcare, and it needs two adults earning between $53,500 and $66,000 to get the $25.30 per week tax cut.
The Council of Trade Unions has worked out just how many families would get that - it estimates about 3000 households would.
"If the National Party disagrees with this analysis, it should show who benefits and when," said CTU economist Craig Renney.
Luxon on Wednesday said he couldn't remember how many families will get the full $250.
National is also disagreeing with some other numbers - the world's largest investment bank, Goldman Sachs, is warning those tax cuts would actually make the cost of living worse by raising inflation.
"I disagree strongly. Our tax plan is fully funded," said Luxon.
But Labour finance spokesperson Grant Robertson said: "For Christopher Luxon simply to say I disagree is not good enough".
"He actually needs to show why it's not true and he hasn't done that."
What both major parties have done on Wednesday is serve up more slams.
Labour's saying the Nats' plan to change benefits would put more children in poverty.
"Chris Luxon, if he wins, the rest of New Zealand loses," said Sepuloni.
The Nats are saying Labour MPs are openly defying their leader with a want for a wealth tax.
"You are seeing very clearly from the Labour Party caucus, you have had three MPs come out over the last 24 hours," said Luxon.
"I think this is a beat up by the National party to distract from the fact their own tax plan doesn’t stack up," said Labour leader Chris Hipkins.
National's campaign chair Chris Bishop took to Twitter to say the Labour Party was lying about offering up Robertson to debate Luxon instead of Hipkins. But The Press' editor has confirmed Robertson was in fact offered up for the debate.
Luxon said there was no "formal appeal for us to debate Grant Robertson".
"Chris Bishop should apologise for that and he should probably just calm down," said Robertson.
National's finance spokesperson Nicola Willis said Bishop doesn't have anything to apologise for.
No scrolls of sorry are being served up today, just some of the scrolls themselves.
