Property research firm Cotality latest preliminary clearance data showed 47.2 per cent of eligible homes sold at auction in the past week.
It was the weakest figure since April 2020, when pandemic lockdowns impacted national auction markets.
The poor result for sellers came despite relatively few properties being put up for auction.
There were 1735 homes under the hammer, down 7.3 per cent on a week earlier and 17.7 per cent down on the same time in 2025.
In Sydney, the nation's most expensive property market, the preliminary clearance rate rose to 53.8 per cent, leading the major capitals.
In contrast, only 26.2 per cent of auctions were successful in Brisbane, the weakest result in the nation, Cotality data published on Sunday found.
Auction clearance rates are considered a key leading indicator for property prices with any result below 60 per cent pointing to a falling market.
Ray White's Thomas McGlynn said buyer behaviour was changing in the final months of the year ahead of another expected interest rate hike.
"With the Reserve Bank's interest rate decision approaching on Tuesday, the coming weeks will be particularly important," he said.
"Buyers are already navigating greater choice and considerable uncertainty, and while the outcome of that decision may influence confidence, it won't change the importance of sellers responding to the market in front of them."
A fifth rate rise for the year would bring the cash rate to 4.85 per cent, the highest level since 2008.
It would also mean a household with a $600,000 mortgage would pay an extra $456 on monthly interest repayments compared to the start of 2026, according to financial comparison site Canstar.
The decline in borrowing capacity, stretched affordability and the federal government's curbs on property investor tax breaks have combined to hit house prices.
Victorian auction figures have also taken a hit after the state rolled out reserve price transparency measures in a bid to stop agent underquoting.
NSW will push ahead with its own reforms with a tranche of changes that kick in from November 17.
Its transparency measures will require agents to include prices in advertisements and keep detailed records to show how they settled on price estimates.
Further changes, to be rolled out in February, will require agents to prepare and present a "statement of information" to explain price estimates.
Underquoting occurs when a property is advertised at a price well below a seller's reasonable estimate of its value.
NSW penalties for the practice will also be increased to $110,000 or three times an agent's commission.
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