Almost a quarter of property investors expect to buy another property within six months.

The further house prices rise, the more risk there is of a big correction, ANZ has warned.

In its latest Property Focus report, the bank's economists have analysed the results of a recent survey of property investors from around New Zealand.

The survey results showed investors were more optimistic about future returns than they had been at any time since 2009. Nearly 60 per cent expect price gains of at least 6 per cent over the coming year.

Almost a quarter said they planned to buy more property within the next six months.

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While they were individually worried about the Reserve Bank's lending restrictions making it hard for them to purchase more houses, they did not seem concerned that the rules could have a wider impact on the market.

Economists including Cameron Bagrie, Philip Borkin and Sharon Zollner said it was not surprising that investors expected North Island centres in particular to experience more of the same house price inflation that they had enjoyed over recent years.

But they said some caution was warranted.

"Given that Auckland has one of the most stretched affordability ratios in the world, any further house price increases from here ups the ante on a correction to bring affordability metrics back into line," they said.

"We could see an outright fall in house prices courtesy of higher interest rates or an economic recession, likely global-led. Conversely, we could see a stagnation of house prices while incomes catch up. The latter would obviously be a preferable adjustment path and that is the path New Zealand has followed before. But with low inflation worldwide it's difficult to envisage inflation and incomes doing the work at the moment. "

They said, if New Zealand went into a deep recession the belief that house prices in this country never fall too far could be sorely tested.

"While owner-occupier property prices tend not to correct downward too far - people just take their house off the market and stay put, the same cannot be said for land prices, apartments or investment properties, which do tend to move in line with the economic cycle."

They said there were growing signs that the Reserve Bank's recent move to restrict lending to property investors had started to cool the property market.

"House sales are down nearly 10 per cent versus a year ago and houses are taking longer to sell, though the market is still incredibly tight. Typically, house prices follow sales with a three- to six-month lag. House price inflation is already easing and we expect it to continue to do so. Given this, investors' house price expectations look overcooked. That said, previous rounds of LVR restrictions proved to have relatively short-lived impacts on the housing market, so investors may be assuming the same will occur this time."

The report said affordability was stretched across New Zealand, with house prices out of whack with incomes. While high debt with low interest rates was okay, high debt and rising rates would not be, the economists warned. But they said there were still too few houses being built to keep up with underlying demand.