Moscow prosecutors have hit TNK-BP with a fresh demand for reams of documents on its foreign employees in an intensification of administrative pressure on BP over its role in the Russian oil venture.

TNK-BP was ordered to comply with the demand to provide an "unprecedented" and "unrealistic" amount of information by yesterday's close of business, people close to the company said. Moscow prosecutors had sent the demand for details on foreign staff last Thursday to Viktor Vekselberg, one of the company's billionaire Russian shareholders, who are locked in battle with BP for control of the 50-50 venture.