Two New Zealand opposition parties, Labour and NZ First, are demanding a register of foreign property buyers as the row over offshore Chinese investors rages on.

Labour leader Andrew Little says New Zealanders need to know exactly how many houses are being snapped up by foreign speculators.

"They're sick and tired of losing homes at auction to higher bidders down the end of a telephone line in another country," he said.

NZ First has drafted a member's bill which would create a register, but it's in a ballot with 74 others and won't be debated in parliament unless it's drawn.

Party leader Winston Peters says Australia started running a register at the beginning of this month, although it only covers farmland.

"NZ First's far more comprehensive register would give New Zealanders information on who is buying what, and from where."

Neither party believes the government's data collection exercise, which starts on October 1, will deliver the information people need.

"From that date, all house buyers will have to have a New Zealand IRD number," Mr Little said.

"That's not the same as a foreign buyers register because there's no guarantee the information will be available in a way that allows public scrutiny."

Labour kicked off the row at the weekend when it released figures from an unnamed real estate firm showing 40 per cent of houses sold in Auckland between February and April went to people with Chinese surnames.

Census data shows about nine per cent of Auckland's population is Chinese, and housing spokesman Phil Twyford says that indicates offshore investors have "a significant presence" in the overheated market.

The government has accused Labour of "playing the race card" in a crude bid to win votes, and at least one party member is reported to have resigned.

3News talked to Phil Quinn, a Labour member for 30 years.

"It's ham-fisted, it's amateurish and above all it's racist," he said.

Mr Little says the resignation is "unfortunate" but the response coming into his office is overwhelmingly positive.