Auckland's median house price has risen a record 26 per cent to $755,000 over the past year, amid signs that supply shortages and surging prices in the city may be prompting buyers to look elsewhere.

The number of houses sold nationwide increased 29 per cent to 7,426 in June compared with the same month a year earlier, according to the Real Estate Institute of New Zealand.

Excluding Auckland, sales jumped 35 per cent.

The national median price increased 5.4 per cent to $450,000 in June compared with the same month a year earlier.

Outside of Auckland the median price was steady at $340,000.

The Auckland property market has been a concern for policymakers due to its supply imbalance, and the Reserve Bank plans to impose lending restrictions on property investors from October, while the government has tasked its tax collection agency to police capital gains more forcefully.

New requirements that all second home buyers must supply a local bank account and New Zealand taxpayer number “may be having some impact at the top end of the market, but for the bulk of the market the trends evident over the past 12 months show no signs of abating,” said REINZ chief executive Colleen Milne.

Labour Party analysis of leaked sales data, said to be from a large Auckland real estate firm, caused controversy over the weekend by claiming close to 40 per cent of the sales appeared to be to buyers with Chinese surnames, prompting accusations of political point-scoring based on crude racial profiling.

“There is increasing evidence that Aucklanders are looking out of the region for properties, both as owner-occupiers and for investment properties,” said Ms Milne.

“Regions such as Northland and Waikato/Bay of Plenty have recorded significant drops in the volume of properties for sale over the past six months, with Aucklanders increasingly being identified as a significant buying group in these regions.

“Further afield, there is increasing evidence that Aucklanders are making up a larger portion of total buyers.”

Ms Milne said prices were continuing to rise in Auckland, where inventory was tight, with less than 10 weeks of stock available.