Realestate.co.nz marketing manager Paul McKenzie said the record shortage was not overly surprising, given how fast the market was moving.
He said it was "a very heated market'' and supply was the main culprit.
"There simply are not enough properties on the market at the moment.''
Mr McKenzie said the traditional winter dip in new listings had also contributed to the record low.
Nationwide, the number of new listings in June was down 5 per cent on the same time last year. There were 9082 new listings last month, the lowest June figure in seven years.
Mr McKenzie said the number of listings, which followed strong new listings in the previous two months, was surprising.
"While we normally see listing numbers fall around this point of the year, the figure is still surprising, especially with the high level of demand from buyers we are currently seeing.''
Asking prices eased slightly last month, with the nationwide average falling to $450,178 - a drop of 1 per cent from the record high seen in May.
In Auckland, asking prices fell 1.3 per cent to $623,471, while in Wellington and Canterbury the asking prices rose 1 per cent, to $451,622 and 410,723 respectively.
The figures were released in the July Property Report, which is compiled monthly by real estate industry website Realestate.co.nz.
Harcourts said that while news listings in Auckland were up a healthy 8.45 per cent on the same time last year, the number of properties available to buy had dropped by 21.82 per cent, showing demand was still vastly outstripping supply.
Harcourts had also noticed a decline in inventory, saying Auckland had enough stock to last four months compared with 5.1 months in June last year.
"Low supply and high prices will continue to fuel the Auckland market until large numbers of housing developments are completed to cope with out growing population,'' it said in its regional marketwatch.
