Doubts over BP’s future in Russia were fuelled last night after four Russian billionaires launched a legal challenge to strip BP-nominated directors of their powers in TNK-BP, the Siberian oil joint venture.

BP faces the risk of losing control of its Russian oil and gas assets as the Russians, who own 50 per cent of TNK-BP, said they would sue the British oil giant in two cities after it rejected an ultimatum to hand them more power in the boardroom.

The move pits BP against four of Russia’s most powerful businessmen in a struggle that may cause BP to lose management control of a business which accounts for a quarter of the British multinational’s oil and gas production.

TNK-BP has accounted for most of BP’s growth in recent years and its creation was a major coup for BP’s former chief, Lord Browne of Madingley. But the venture has been the target of a relentless Kremlin campaign to force BP to cede power to a state-controlled rival, such as Gazprom or Rosneft.

Escalation of the TNK-BP conflict will raise further concerns about Russian oil production, which has been shrinking this year. Concern about Russia’s output has contributed to the surge in oil prices.

The Russian shareholders — Viktor Vekselberg, Mikhail Fridman, German Khan and Len Blavatnik — said that they would sue BP in Stockholm and in Moscow in an attempt to strip BP-nominated directors of their powers.

The move came after the expiry of a deadline they had set for BP to bow to their demands for greater representation on TNK-BP’s boards and fewer BP secondees at the company.

The Russians’ AAR consortium argues that BP has violated an agreement on the use of foreign secondees by drafting in large numbers of staff to managerial positions in Moscow rather than to technical posts in the field.

“We will be asking the International Arbitration Court in Stockholm to declare the secondment agreement null and void. We have made a decision to file the suit today,” an AAR spokesman said.

TNK-BP employs 148 BP staff under the agreement, but they have been unable to work since Tetlis, a little-known investment vehicle, filed a lawsuit against the company in a court in Siberia. BP suspects that the suit was inspired by Mr Fridman’s Alfa Group, pointing out that two of Tetlis’s senior managers used to work for Alfa. Alfa denies any involvement.

The billionaires plan to ask a Russian court to strip BP nominees of their powers for holding an allegedly illegal board meeting. BP has rejected the charge, saying that the board meeting complied fully with Russian law.

An AAR spokesman claimed that BP had urged them to sell their stake in TNK-BP, which made net profits of $5.3 billion (£2.7 billion) last year. A BP official denied this and claimed that the billionaires had asked the British side to buy their shares. He added that it had agreed to do so only with Kremlin approval and an agreement on the onward sale of the stake.

BP paid its partners $6.75 billion for a 50 per cent stake when the joint venture was set up in 2003, in what was then the largest foreign investment in Russia. TNK-BP accounts for a quarter of BP’s worldwide output.

The legal action began after the breakdown of negotiations yesterday to resolve the dispute.

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