Macfarlanes has been called in to advise mining giant Bumi on an investigation into alleged financial irregularities in its Indonesian operations.

The City firm is understood to have been instructed by the company yesterday (24 September), when Bumi announced the internal investigation into its Indonesian subsidiary PT Bumi Resources, in which it has a 29% stake.

The investigation will look at alleged irregularities in the company's development funds, with millions of dollars thought to have been diverted and some funds' value written down to zero by the close of last year.

Announcing the investigation Bumi said: "An independent investigation has been commissioned to investigate the allegations on an urgent basis, and is to report to the board. The company also intends to contact relevant authorities in the UK and Indonesia, as appropriate, in respect of some of the allegations.

"An area of focus of the investigation will be the development funds of PT Bumi Resources Tbk. The extensive development funds in PT Bumi Resources Tbk and the one development asset in PT Berau Coal Energy Tbk were marked down to zero in the accounts of Bumi plc as at 31 December 2011, except for one investment with a carrying value of $39 million in the consolidated financial statements."

Non-executive director of Bumi, Ari Hudaya, resigned yesterday after the probe was announced, with share prices in the company plummeting by around 25% by the end of the day.

The news comes after Berwin Leighton Paisner (BLP) and Slaughter and May advised on the $1bn (£632m) sale of a 24% stake in Bumi in February this year.

BLP advised the sellers, commodities trader Bakrie & Brothers and Indonesian investment company Long Haul Holdings, while Slaughters acted for the buyer, coal mining company Borneo Lumbung Energi and Metal.

Created by financier Nat Rothschild, Bumi has come under repeated scrutiny over the last year for poor corporate governance, flagged by Rothschild himself. The move saw him ousted as co-chairman from the company.

Much of the scrutiny over governance has related to one of Bumi's largest shareholders- the Bakrie family.
Meanwhile, Freshfields Bruckhaus Deringer and BLP took lead roles in June 2011 on natural resources giant Vallar's $2bn (£1.2bn) issuance of convertible bonds to acquire a 75% stake in Bumi Resources Minerals.