In a statement the head of the Kazakh financial police, Sarybai Kalmurzayev, said, “BG-Karachaganak had smuggled unstable gas condensate worth some 370 billion tenge (US$2.7 billion) to Russia in 2001-2003.”

“The damage inflicted to the state is worth 735 million tenge (US$5.4 million) [and] I believe [investigating] the Karachaganak case is a matter of a few months,” added Kalmurzayev.

The British firm has confirmed investigations by the Kazakh authorities are underway.

“As part of routine business investigations, we were subject to an audit in March, which raised issues with respect to appropriate processing arrangements and associated customs requirement,” said the Group.

“We have formally responded to all points raised in the audit and are co-ordinating with the authorities,” it added.