Sydney led a national housing market downturn, tumbling 1.4 per cent in July alone as premium properties took the brunt of the fall with a 1.8 per cent decline.

Auction listings dropped nearly 20 per cent across major capitals, even as property investors raced to buy before the self-managed super fund borrowing ban.

Property values have racked up their biggest fall since Anthony Albanese took office as rates, cost of living and tax changes collide.