Any attempt to solve Auckland's housing demand crisis needs to dampen property speculation by both domestic and international buyers, the Green Party said today.

"Rampant property investment, not ethnicity, is driving up demand for Auckland houses," Green Party Co-leader Metiria Turei said.

"Non-resident foreign buyers should be prevented from investing in the New Zealand housing market, but if parties are serious about dampening the demand for Auckland property, they need to deal to tax incentives that are encouraging locals to invest in property too.

"There are more than 300,000 landlords in New Zealand, and up to 40% of all Auckland property transactions involve investors.

"Though we agree with Labour that speculation by non-resident foreign buyers is a problem, it's only part of the problem. In Government, the Greens would push for a capital gains tax on all properties except the family home, to encourage Kiwis to invest in more productive industries, and free up more homes for first-home buyers.

"The Green Party is the only major party that has consistently pushed for a proper capital gains tax on properties other than the family home. Young Kiwis trying to get into the housing market need political parties to be brave and to back them.

"The Government's new 'bright-line' test won't stop people throwing money at Auckland houses, then flicking them on for a massive capital gain.

"Until tax incentives to invest in the property market are dealt with through a proper capital gains tax on the sale of all properties other than the family home, Kiwis and foreign investors will still be encouraged to lock away their money in property," Mrs Turei said.