Three economists have teamed up to scrutinise part of National's tax plan.

The party's proposed ending the ban on foreign buyers - for homes worth more than $2 million- and taxing them 15 percent.

It expects foreigners will buy 1700 houses valued on average at around $2.9 million.

But economist Michael Reddell says it'll be more like 700 in that price range.

"That $2 million threshold really does matter, because average house prices - even in Auckland - are well below $2 million. And there just aren't that many really expensive houses in New Zealand."

LISTEN ABOVE