A mortgage company adviser says first-time home buyers will be the hardest hit by changes to banks' lending criteria.
From September, the Reserve Bank will require banks to hold 12% more capital against the mortgages of borrowers who have deposits of less than 20% of the house price.
Bruce Patten told Morning Report the Reserve Bank now has the tools to force the four major banks to require a bigger deposit.
But he said it has picked on first-home buyers, when there are plenty of other buyers it could be looking at - such as property investors, who are pushing up prices, and people trading in properties.
Mr Patten also said overseas investors, including New Zealanders living overseas, are contributing to soaring house prices.