The Real Estate Institute of New Zealand ("REINZ") reports that the number of residential property sales in January reached their lowest monthly level since 1992, suggesting that the housing slump continues to deepen.

The national January median of $325,000 was down 4.4 per cent from $340,000 in 2008, and the $327,000 median in January 2007.

However, REINZ president Mike Elford said well priced properties coming on the market were selling and holding their value to a "reasonable degree".

"Of greater concern is not the price of houses, but the very limited turnover," he said.

The 3706 home sales nationwide in January were significantly down on the 5186 in January 2008, and also down on the 4302 in December.

Before 2008 the lowest turnover was in January 1992 when 4427 houses were sold.

Falling interest rates had yet to revitalise the market.

Another worrying trend was the length of time being taken to sell a house, reaching a national median of 59 days last month, compared to 49 in January 2008 and 45 days in December, Elford said.

The number of days taken in January was the most since January 2001 when houses took on average 64 days to sell.

Taranaki was the only region not to have a drop in median house prices last month, with a rise of 1.4 per cent to $266,750.

The biggest drops were in Southland, which fell 22.2 per cent to $175,000, and Northland down 16.2 per cent to $275,000.

Sales turnover had been relatively flat since mortgage rates began declining in the second quarter of 2008, so at the least lower rates appeared to have put a floor under sales activity.

ASB expected house prices would continue to gradually fall during much of 2009.