The company has been implicated in a scandal involving an oil-trading company, Qingdao United Energy. It is claimed that trader Zhang Wei arranged illegal deals with a worker at Trafigura.

According to reports, Zhang bought 700,000 barrels of petrol from Trafigura at the market price using letters of credit issued by Qingdao, and then sold them back to Trafigura at a discount of $32m.

A senior Trafigura source told Reuters that the company believed Zhang was the authorised agent of Qingdao and that he had represented other companies in previous transactions without problems.

As far as we are concerned, there is no change in the substance of this matter, which is a commercial dispute and not a matter for police or state prosecutors,” the source said.

“We believe the prosecutors will conclude there are no charges to answer, but if any are brought we will vigorously contest them.”

A Trafigura employee, Tian Meng, has been held by police since August and can be detained for seven months without being charged.

The frozen accounts are believed to be held with Industrial and Commercial Bank of China and Bank of China, and are owned by Trafigura Private Ltd, the company’s Singapore unit.

Trafigura declined to comment yesterday.

The company, one of the world’s biggest privately-owned oil and metals traders, is best known in the UK for seeking to kill a story about its illegal dumping of hazardous waste by gagging the press with a super-injunction.