One in seven houses sold in Auckland's fiercely competitive housing market are being bought by people who already own five or more properties, new data shows.
This group of multiple property owners have increasingly swallowed up more of the city's houses over the last four years, mostly at the expense of people looking for their first home.
The trend surprised property investment groups who say recent Government and Reserve Bank restrictions have made it harder to invest in residential property in the city.
But the Labour Party says it is further evidence that Auckland remains a property speculator's paradise and that new controls are needed.
Data compiled by Core Logic shows the share of Auckland houses being bought by people with five or more properties has grown by 40 per cent since 2012, after remaining steady for the previous seven years.
People in this category bought nearly 6000 out of 45,000 houses sold in the city last year. Nearly half of these homes went to people who already owned 10 or more properties.
In the year to date, people with five or more homes have bought 3451 additional houses, or 14.8 per cent of all houses sold in Auckland. That compares to 10.7 per cent in 2012.
Labour's shadow housing minister Phil Twyford said the data showed that speculators had been allowed to "run riot" in Auckland, at the expense of first home-buyers.
"Since 2012, when the market really started to heat up, we've seen a 40 per cent increase in sales going to investors with five or more properties."
Investors already face some restrictions in Auckland, in particular a requirement that they pay a 40 per cent deposit.
Labour wants the Government to go further and get rid of negative gearing, which allows landlords to claim a tax break on rental losses.
The policy was also favoured by half of business leaders in the Herald's Mood of the Boardroom survey.
The Government says it is unlikely to remove negative gearing for rentals.
Revenue Minister Michael Woodhouse said ring-fencing rental property losses was previously scrapped in New Zealand because it had too many loopholes, and he had no plan to reinstate it.
"If the goal is to curb house price inflation, the sorts of things we've seen haven't been effective in other jurisdictions."
The policy would also drive up rental prices, he said.
Woodhouse noted that the Government had already acted in this area, by removing the ability to claim depreciation on rental homes in 2010.
Auckland Property Investors' Association president Andrew Bruce said he was surprised that people with large property portfolios were still playing such a large role in the Auckland market.
Many of the big investors had moved their interest outside the city after the Reserve Bank began clamping down on lending, he said.
Bruce also argued that those with many properties were not solely responsible for Auckland's rising prices and a shortage of housing.
"A lot of people that are actually driving the market, the fear-of-missing-out people, that have been down to the local barbecue going 'Christ, this person's just bought a house a year ago and they made x amount of dollars, I better jump in before I miss out'."
Gary Lin, a 33-year-old civil engineer who owns 11 rental properties in Auckland, said it was getting "harder and harder" to invest in property because of high prices and restrictions on lending.
But it remained the only reliable, stable investment, he said, and investors still received favourable tax treatment.
"I understand people might be bitter," Lin said about his large property portfolio.
"The thing is that we live in a capitalist world ... and there's nothing illegal about it."
Because he "bought and held" rental properties rather than selling them for the capital gain, the new lending restrictions and the "bright line test" had not affected him.