Economists across the political spectrum have found the National Party's tax plan has an enormous hole in it.
Their concerns centre on the proposed foreign home buyers tax - which National is relying on to raise $740 million a year.
But using real estate data from Corelogic, the economists have calculated that revenue will fall short by some 60 to 70 percent.
Former Reserve Bank economist Michael Reddell is one of those economists.
Riddell spoke to Corin Dann.
