The Labour Party has admitted its figures on the number of overseas-based house buyers are crude but says they are the next best thing in the absence of government-collected data.
Labour has said it is not backing down on its suggestion that foreign Chinese buyers are flooding the Auckland market.
It has been criticised for using three months of data to infer people with Chinese names bought 40 percent of properties sold by one Auckland real estate agency.
Mahon China Investment Management director David Mahon, who is a property investor in China, said real data on foreign buyers was needed before primitive generalisations were made. He said property speculation was a real issue but racist arguments did not help.
"The trouble with the current debate is that it is rather primitively centred around Chinese buyers because they're an easy group to single out, because they look different, they speak another language," he said.
"I wonder if we looked at all statistics of foreign buyers over a real period of time, how many people from the United Kingdom for example have been buying houses in New Zealand?"
Mr Mahon said some in China were perplexed as to why New Zealand's property market was so open to foreign buyers.
Labour leader Andrew Little said that the party's figures were verified and credible and in tune with anecdotal evidence from auction rooms around the city.
"There are people on the end of a phone who are not resident here, don't make a commitment to New Zealand but want to buy property here, who are shutting others out of buying a house in Auckland, including Chinese residents and citizens in New Zealand."
He said the data release was justified and in the public interest given the problems with the Auckland housing market.
Listen to Andrew Little
But the Minister for Economic Development, Steven Joyce, said the Labour Party would pay at the polling booths for many years to come for taking cheap political shots at Chinese people.
Mr Joyce told Morning Report that Labour had simply picked on people with Chinese-sounding names and the data was "completely irrelevant".
"What the Labour Party has done is say, 'We're going to take a cheap political shot at an ethnic group of New Zealanders now - even though the data is coming up soon - we're going to have a go at them now because of their surnames'," he said.
"Now, if the National Party had done that at any time in the last 20 years, the liberal intelligensia would be tearing the house down."
He said reliable data would start being collected in October, although he was unable to say when that would be made publicly available.
Listen to Steven Joyce