Labour's making a big effort to cast doubt over the foreign buyers tax element of National's tax policy, calling it a 'voodoo money fantasy plan'.
But there are legitimate questions being raised about where the buyers are coming from and what it'll do to the housing market.
In Auckland Central, almost one in five homes used to be sold to foreigners. But the red light on overseas buyers would be turned green if New Zealand gets a blue Government.
The foreign buyers would be taxed.
National would only let foreigners buy homes over $2 million and they'd be taxed 15 percent.
"Other jurisdictions have taxes on foreign purchasers at a range of levels. Vancouver 20 percent, NSW 8 percent," said National's finance spokesperson Nicola Willis.
Those are two of the most expensive places in the world for housing.
"The two issues are not linked," said National leader Christopher Luxon.
"What we're saying very clearly is that actually what you see when you see tax buyer taxes, or foreign buyer taxes, put in place. We think that's really to stop speculation."
National's entire tax plan depends on sucking $3 billion out of foreign buyers over four years.
"Our modelling assumes fewer than 2000 transactions will occur," said Willis.
In one year. there were 4244 houses sold for more than $2 million. So National needs half of those to be to foreign buyers and then for them to keep buying and buying and buying.
"It's a big chunk of the overall support for this programme. The reality is we have no evidence to support that this money will turn up," said Council of Trade Unions director of policy and economics Craig Renney.
If or when it does, Labour says it will drag up house prices combined with National's promises of tax breaks for landlords and letting investors sell houses tax-free after two years - instead of 10.
"Then there comes to the housing market, which National will be pouring petrol on. They will lock first home buyers out," said Finance Minister Grant Robertson.
Infometrics principal economist Brad Olsen said: "There might be some potential for house prices to go higher than they might otherwise, there's also the potential that rents might not increase like they might otherwise."
Foreign buyers and immigration are two cornerstones of National's tax plan and so as sure as the sun rises, Winston Peters the protectionist rose.
In a statement, the NZ First leader slammed what he's calling a foreign buy-up which doesn't stack up.
Asked if he was giving Peters another platform to run on, Luxon replied: "What we're talking about here - and I think it's really important for you to understand - is it's not political, we're actually here to deliver and help the squeezed middle of New Zealand."
