Peter Thompson, Barfoot managing director, told TV One's Sunday programme that 40 per cent of auction sales were to people of Asian ethnicity.
Asked where exactly these people came from, Mr Thompson said: "That's hard to say. Are they New Zealand-born Asian? Are they Asian people that have moved to New Zealand with permanent residency? Or are they in fact offshore Asians?"
Twenty out of Barfoot's top-25 grossing agents were of Asian ethnicity, a fact he attributed to job dedication, saying they worked up until 2am while other agents probably finish at about 9pm.
Australian buyers were active here too though, he told the Herald.
"Asians you can pick, whereas it's hard to pick Australians, English and Americans. We've noticed a lot of Australians coming over," he said.
The BNZ-REINZ survey interviewed 549 agents, 212 of whom were from Auckland. Mr Montgomery said he did not know of any Australians buying in Auckland and the survey did not take a big enough sample.
"The Government can't tell because it doesn't collect the data so it can't make any policy decisions on it," Mr Montgomery said.
But BNZ chief economist Tony Alexander stood by the results.
"The survey is big enough to be valid in terms of the results. People are saying there are a greater number of Asian buyers but no one has the ability to say whether they're New Zealanders, migrants, [or] flown in from overseas," he said.
The survey was the only database which sought to quantify foreign house buyers, he said.
"There is no information on foreign purchasing of houses in New Zealand beyond that survey and much more work needs to be done before one can say definitively what the actual proportion is. More than a simple survey is needed for that.
"There is no information on the proportion of the housing stock ... owned by foreigners and certainly zero information on any of the characteristics of any of the foreign groups buying houses in New Zealand."
Helen O'Sullivan, Real Estate Institute chief executive, was not surprised about Australians featuring prominently in the survey, saying New Zealanders also bought houses across the Tasman.
"Australians like our market for its simplicity, no stamp duty, familiarity and proximity," she said.
"The survey results are indicating that while there are foreign buyers active in the New Zealand market, they are from a number of sources and unsurprisingly those tend to align with the sources of our international relations and trade like Australia, Asia, Europe."
Read also:
Call to limit foreigners' right to purchase homes
Prejudice is the main fear
Some turn up to bid, and others merely to watch