The Australian stock market hardly reacted to the Reserve Bank of Australia's surprise move to keep interest rates on hold for the fifth straight month, and are still trading lower, after US and European equities ended weaker.

In afternoon trade, the benchmark S&P/ASX200 index lost 43 points, or 0.9 per cent, at 4582.3. The broader All Ordinaries index had slipped 41.3 points, or 0.9 per cent, to 4637.1.

The big four banks were in the red, as ANZ Banking Group edged back 18 cents at $23.50, Commonwealth Bank of Australia lost 53 cents to $51.01, National Australia Bank gave back 16 cents at $25.29 and Westpac Banking Corp gave back 27 cents to $23.05.

Meanwhile, investment bank Macquarie Group slumped 60 cents to $35.85.

The miners also fell, with BHP Billiton losing 54 cents, or 1.4 per cent, at $39.46 after a report from a Canadian think tank said the miner's takover of Potash Corp could cost the province of Saskatchewan $C2 billion ($2.02 billion, $US1.96).

Rival Rio Tinto fell $1.34, or 1.7 per cent, to $76.74 and junior miner Fortescue Metals Group dropped 5 cents, or 1.9 per cent, at $5.23.

The RBA surprised the market on Tuesday by keeping the official cash rate at 4.5 per cent and granting borrowers a reprieve.

Analysts had expected an increase of 25 basis points given the nation's solid trade surplus, a 20-month high in job advertisements and unemployment level of just 5.1 per cent.