House prices increased in every region in July – with the one exception of Auckland, new figures reveal.

National house prices rose 6.2 per cent in the July year but Auckland prices are continuing to fall slightly, down 0.1 per cent in the same period.

The Real Estate Institute has just released data showing that excluding Auckland, national house prices rose 8.6 per cent in the July year, from $419,000 to $455,000.

In Auckland, prices fell by $1000 from a median $836,000 a year ago to $835,000 last month.

Four regions had record prices in July: Northland (+5.7 per cent to $481,000), Taranaki (+15.4 per cent to $375,000), Nelson (+15.2 per cent to $547,000), and Marlborough (+13.4 per cent to $453,500) – the second record month in a row.

Bindi Norwell, REINZ chief executive, said the shortage of properties for sale was continuing to push prices up in all regions except for Auckland.

"With July producing another four regions with record median prices we desperately need to increase the supply of new houses – be that through KiwiBuild or from private developers and builders – in order to fill the significant shortage of properties around the country," Norwell said.

"Auckland continues on its steady trajectory with only minor changes in median price each month. Auckland and North Shore cities saw median price decreases of -1.6% and -1.3 per cent respectively to $892,000 and $985,000. However, Waitakere City saw a median increase of 4.6 per cent to $774,000 highlighting the popularity of this more affordable part of Auckland," she said.

"The stability of Auckland's median price will be welcome news for first-time buyers struggling with Auckland's house prices, but time will tell whether the low to mid $800,000 mark is a longer-term trend," said Norwell.

The number of houses sold in New Zealand during July increased by 0.7 per cent or an additional 42 properties when compared to the same time last year, from 5619 to 5661.

For New Zealand excluding Auckland the number of properties sold increased by a marginal 0.2 per cent or just an additional seven properties compared last July, from 3942 to 3949, REINZ said.

Economic commenters have said that while winter is traditionally slow, a slump across the Tasman has heightened concerns that we may see price falls here for the first time in several years.

But in Auckland, where prices have been flatlining for more than a year, the prospects of prices slipping further into negative territory looks increasingly real and Reserve Bank Governor Adrian Orr has warned of that possibility.

"We're within a wisp of that happening in Auckland housing prices at the moment," Orr told TVNZ's Q+A at the weekend.

Barfoot Auckland and Northland house price data released on August 3 showed much the same pattern as REINZ: an average sales price in July of $912,487, down 1.8 per cent on June this year.

Barfoot managing director Peter Thompson said: "July is traditionally when prices reach their low point for the calendar year and with sales numbers holding up the signs are there that not only is the market weathering winter well, it is setting itself up to be active in the coming spring."

For the fourth consecutive month, Auckland house sales were in excess of the number for the corresponding month for the previous year, he said

"Sales numbers are definitely higher than they were last year and with 830 sales in July were 11.1 per cent higher than in July last year," Thompson said on August 3.