An Auckland property manager is warning of a looming rental housing crisis - but his claim has been rejected by market watchers.

Wayne Boberg of property management business Bobergs First National tracks the rental and houses for-sale markets and said the Government's tax change proposals were encouraging a rental property sell-off.

"Since the Government raised the issue of property tax changes in August last year, there has been an increase in the exodus of landlords from the rental market, mainly landlords who have been in the market for a long time," Mr Boberg said.

"They have sold their properties to owner-occupiers so those homes are lost to the rental market."

But the principal economist at the NZ Institute of Economic Resesarch, Shamubeel Eaqub, said assertions that landlords were quitting the market were wrong.

And Peter Thompson of rental managers and agents Barfoot and Thompson said property management was a growing business for his firm.

Barfoots had 8610 landlords and managed 9500 tenancies, up from 8017 landlords and 8900 tenancies a year ago.

January and February were particularly busy as students demanded rental properties, Mr Thompson said. He did not expect the situation to change.

Mr Eaqub said the crisis suggestion did not make sense.

"He had cited a halving of listed rental properties since late last year. Over the same period, Barfoot and Thompson increased the number of properties rented by 3 per cent," Mr Eaqub said.

Mr Boberg said fewer houses were available for rent, but many of those left had rising rents.

"We are finding the demand for rental properties is not diminishing and rents for even ordinary properties are rising," Mr Boberg said.

A two-bedroom Blockhouse Bay house rented for $225 a week was vacant shortly before Christmas. The landlord cleaned it up and improved the kitchen and it was now rented at $265 a week.

Mr Thompson said rental property was always in strong demand and his firm was consistently letting more than 700 properties a month.

"No decision on tax changes has been finalised," he said. "I'm not saying it won't happen but it's just a proposal at the moment.

"We must be doing something right because our property management division is expanding."

Last month, Barfoot let 705 houses and units, down 10.1 per cent on January and 10.3 per cent on February last year.

In rent patterns in recent years, February's rents had fallen from a high in January, and then edged up again in March and April, Mr Thompson said.

"There is a steady demand for rental properties but limited availability across most geographic areas and price ranges. The area of greatest shortage is in quality, executive homes with three or four bedrooms."