The Australian sharemarket is trading sharply lower at Thursday noon after receiving some mixed local data and negative leads overnight.

Around midday, the benchmark S&P/ASX200 index had slipped 48.7 points, or 1.1 per cent, to 4596.3 while the broader All Ordinaries index had fallen 45.1 points, or 1 per cent, to 4648.9.

All sectors lost ground, but the finance sector was the worst-off, reversing 1.4 per cent, following reports that ratings agency Fitch is set to conduct stress tests to measure the impact of rising house prices on local banks' debt.

Materials declined 0.8 per cent and energy shares dropped 1 per cent.

Among the major banks, National Australia Bank gave back 1.19 per cent to $25.59.

Westpac backtracked 45 cents to $23.26. ANZ Banking Group slipped 1.9 per cent to $23.68, and Commonwealth Bank surrendered 63 cents to $51.42.

Investment bank Macquarie Group dropped 1.78 per cent to $36.34.

Top miners BHP Billiton and Rio Tinto initially climbed after copper increased to a more than two-year peak, with prices in London above $US8000 a tonne.

But resources stocks gave up early gains, on news BHP Billiton and Rio Tinto are looking at revising or postponing their proposed $US116 billion ($A120 billion) iron ore joint venture.

BHP Billiton was recently off 13 cents at $39.24, and Rio Tinto sagged 18 cents at $77.08.

Fortescue Metals Group bucked the trend, improving 0.97 per cent to $5.20.

Gold producer Newcrest Mining softened 0.85 per cent to $39.66, despite the price of gold setting its tenth record in 12 days overnight.