BHP Billiton Ltd, the world's biggest miner, has said that its annual profits plunged more than a third as a slowdown in global economic growth led to weaker prices for its key commodities.

The company blamed its performance on sharply lower commodity prices and high write-downs on its shale gas and nickel assets.

Net profit for the 12 months to June 30 was $15.4 billion, down 34.8 per cent from $23.6 billion in the same period a year ago, Melbourne-based BHP said in a statement.

Revenue for the year rose 0.7 per cent to $72.2 billion, from $71.7 billion last year.

Immediately after releasing the results, BHP announced it was delaying a plan for a massive $30 billion expansion of its Olympic Dam uranium and copper mine in southern Australia.

CEO Marius Kloppers cited lower commodity prices and higher capital costs as reasons behind the delay. The company said it would explore the possibility of a less expensive expansion instead.

In the short-term, BHP said it anticipates more volatility in commodity markets amid weakness in the manufacturing and construction sectors.

"However, in the medium term we expect supportive economic policy and a broad growth bias, particularly in China, to lead to measured improvement in the external environment beginning in the first half of the 2013 financial year," the miner said.

BHP declared a final dividend of 57 cents a share.