Prime Minister John Key says he potentially supports income-related restrictions on mortgage lending.
Mr Key said increasing supply was still the main issue to dampen the overheated Auckland property market, but the Reserve Bank had some options to address the demand side.
Investors account for about 46 per cent of property transactions in Auckland.
Mr Key, who again resisted labelling the Auckland housing situation a crisis, said the Government had introduced the bright line test to target investors but the Reserve Bank could take further action.
"I think it's one of the issues the Reserve Bank can give some consideration to, because they can target groups, just like they did with their LVR ratios, and they are looking at income ratios, they have the capacity to look at that," Mr Key told Radio New Zealand.