Mr Thompson would not say whether the company had already contacted lawyers and refused to comment when asked if Barfoot had launched an internal investigation in a bid to identify the source of any leak.
Newstalk ZB reported that he had questioned the figures used by Labour housing spokesman Phil Twyford, saying they were arrived at by tallying up Chinese-sounding names. He said that was akin to assuming anyone with the surname O'Brien was Irish.
The data was analysed by matching buyers with surnames that were ethnically Chinese. It is not known from the data if the Chinese buyers were based here or overseas.
Warning in memo
Mr Twyford told the Herald that he had not heard from Barfoot and Thompson's lawyers yet. "What any real estate agent does is up to them," Mr Twyford said of Mr Thompson's statement.
"My beef is with the Government who have cynically refused to set up a register of foreign ownership and share the information with the public," Mr Twyford said.
However, it is also understood Mr Thompson has released a detailed memo to all staff today, reminding them of their obligations and duties and referring to the information leaked to Mr Twyford, then passed to the Herald.
Mr Thompson's memo is understood to alert staff to the fact that they must not disclose any internal figures or data to anyone and that every agent must act in the interests of their vendors.
In the Herald's weekend report Mr Twyford said that the data, which represents 45 per cent of all Auckland sales over the three months, showed for the first time the scale of an issue that was pricing first-home buyers out of the market.
"It's staggering evidence that strongly suggests there's a significant offshore Chinese presence in the Auckland real estate market. It could not possibly be all Chinese New Zealanders buying; that's implausible," he told the Herald at the weekend.
Call to follow Australia
Barfoot & Thompson's response to the data came as BNZ chief economist Tony Alexander has called on New Zealand leaders to require foreigners to build new places rather than buy existing Auckland houses.
Alexander wrote in his latest newsletter that New Zealand would do well to follow Australia's example and put restrictions on foreign buyers.
"We should as soon as possible adopt Australia's rules restricting foreign buying of anything other than new housing unless resident for 12 months," Alexander wrote.
Alexander called for more information on the topic.
"I do not fault Labour's housing spokesman Phil Twyford for releasing the data. But as with my own efforts to estimate offshore buying last year and in 2013 the data simply do not allow us yet to truly know what proportion of our housing stock is being sold to people who will never live here - be they Chinese, Albanian or whatever," Alexander said of the BNZ-REINZ survey.
He warned that requiring foreigners to build houses was not the absolute solution.
"Adopting Australia's rules as they stand won't be the panacea many are hoping for. In Australia's case people have been able to get around the restrictions quite easily. The regime is now being enforced more rigorously, but that does not necessarily alter what is being seen as a huge problem - something which people in Hong Kong have been seeing more and more of in recent years."
Housing minister Nick Smith has dismissed Labour's housing data but said the Government's newly introduced requirement for all house buyers to have an IRD number and a New Zealand bank account from October would give far more accurate information on the extent of overseas investment in Auckland housing.
Stock market fears
The revelations come amid warnings that rich Chinese investors will be looking to take their money out of China's turbulent stock market and invest it in property overseas.
The Guardian reported that estate agents in Australia, Britain and Canada are expecting a surge of interest from Chinese buyers.
Last month, the Herald reported that China's easing of restrictions on privately held capital could result in Chinese buyers pouring US$10.9 billion into New Zealand real estate.
A report from real estate listings website Juwai.com, with 2.5 million properties and businesses for sale, studied the effects of the Chinese government's second phase of its Qualified Domestic Individual Investor (QDII2) programme to allow its citizens to buy overseas property.
Andrew Taylor, Juwai.com's co-chief executive, said rich Chinese were drawn to New Zealand.
"Juwai.com projects that the pilot program will enable US$11 billion of new Chinese money to flow into New Zealand's real estate market. That's based on wealthy Chinese investing 10 per cent of their assets into international property, including commercial. It's also based on NZ getting about 3.3 per cent of that property-specific investment, as it has in the past," he said.
What the data shows
The leaked data
• Labour received leaked figures covering 3,922 Auckland property sales by one real estate firm from February to April this year. It carried out its own analysis on the figures, using surnames combined with other data.
• Labour used a statistical technique called Bayesian analysis to estimate ethnicity from surnames. This combines a number of data sets, including Census meshblock data and the electoral rolls database, to estimate the probability of whether a name is European, Maori, Chinese, et cetera.
• The analysis cannot prove statistically whether a buyer is a foreigner or local. Labour's view that most buyers must be from overseas is based on the fact that ethnic Chinese make up only nine per cent of the population but 39.5 per cent of the house buyers. However the Census figures are from a large base of 1.4 million people, whereas the house buyers data is from less than 4,000 sales.
• The data comes from one agency and does not show sales by other agencies. It does however contain 45 per cent of the sales in that period in Auckland.
• The Weekend Herald has seen the leaked sales figures data and reviewed Labour's methodology. The party updated its figures based on our feedback. We were not able to redo the analysis independently, as it relied on data sets such as the electoral rolls database, which is only available to political parties.
