Chinese companies have used falsified gold transactions to obtain more than Rmb94bn in loans since 2012, according to the country’s national auditor.

The fraud, involving 25 bullion processing companies, was cited in the National Audit Office’s annual report to legislators this week and has raised further concerns about the integrity of China’s commodity markets.

An inquiry was launched this month in the northeastern port city of Qingdao following allegations that a metals company had pledged the same stocks of copper and aluminium multiple times as collateral for loans. Other commodities, including soyabeans, iron ore and rubber, are also routinely used in financing deals struck with local and foreign banks in order to circumvent tight domestic credit conditions.