TNK-BP, the Anglo-Russian oil joint venture, is bracing itself for a full investigation within weeks into its licence agreement for a giant Siberian gasfield as the Kremlin tightens its grip on the country's energy resources.

Russia has used environmental audits and regulatory threats to restore state dominance over oil and gas supplies. This week saw Gazprom take a controlling stake in Royal Dutch Shell's Sakhalin-2 project after months of pressure.