He said the data for March had shown rapid growth in house prices continued through most of the country - and the strength dramatically returned to Auckland.

Stephens said the fact that new loan restrictions and rules around capital gains had only had a temporary effect when they were introduced at the end of last year was not a surprise, but many people had been taken aback by how quickly Auckland's market had taken off again.

Real Estate Institute figures show year-on-year,  seasonally-adjusted, Auckland's median price rose by 7.7% in March to hit a new record high of $820,000. Sales volumes were also up by 66.8% on February, although they were down by 21% on March 2015.

Stephens said low mortgage rates were driving price rises, adding fire to the impact of population growth and a strong economy.

"The evidence that these low rates are playing a role is the fact that households are taking on more debt, the debt-to-income ratio has risen to a record 162% of GDP."

That made it unlikely that the Reserve Bank would want to cut the official cash rate again at its next meeting, he said, but meant it might consider other ways to cool the market.

It has been suggested that investor-specific loan-to-value rules could be introduced in other parts of the country.

"[This] increases the chance the Reserve Bank will at least talk about new LVR restrictions," Stephens said.