According to industry rules devised by the US Securities and Exchange Commission (SEC) BP replaced 89% of the oil and gas it used last year. This was reduced to 78% when stripping out partners such as TNK in Russia.

The SEC insists companies use the year-end oil price when calculating reserves.

But a growing proportion of reserves is held in production-sharing contracts with governments and state-own ed entities, in which companies are paid their share in barrels of oil. With higher prices meaning companies own fewer barrels of oil, the year-end crude price of $40 led to most companies cutting reserves.

BP has said it makes more sense to use their long-term price assumptions of $20 when calculating reserves, the figure it uses when investing. Under UK rules, which allow for the use of the $20 price, BP replaced 110% per cent of the oil and gas extracted.

BP chief executive Lord John Browne said BP and other companies had commissioned consultancy Cambridge Energy Research Associates to make recommendations on how to end the confusion. The report is due on 23 February.