Mumbai: British oil giant BP and its Russian partners are battling for control of their $40 billion equal joint venture, TNK-BP, Russia's third-largest oil producer and a key oil reserve for the international energy giant.

TNK-BP was set up as a 50-50 venture between BP and three Russian firms - Alfa Group, of which Fridman is chairman; Renova Group and Access Industries in 2003 with an investment of $7.5 billio from BP.

Russian tycoon Mikhail Fridman, one of the Russian partners, charged BP of stifling growth at TNK-BP by treating it as a subsidiary and demanded sweeping changes in management.

Fridman cited TNK-BP's dismal performance vis-a-vis other Russian energy companies and BP's rejection of 20 international projects on grounds that they would compete with other BP projects.

Fridman also threatened to file a suit in Russian court to stop TNK-BP's annual general meeting on 26 June and said he would try all ''legal means'' to dismiss TNK-BP's chief executive, Robert Dudley.

"Any other board would have dismissed its CEO a long time ago, and any other 50 per cent shareholder would have initiated legal action to ensure that directors perform their fiduciary responsibility," Fridman said. "We need foreign investors that will help ensure the growth of Russian companies, not constrain their development," he added.

He said TNK-BP should have an independent chief and not someone who takes orders from BP.

BP, however, maintained that the Russians have been orchestrating tax investigations and raids by security agents on the company's offices to wrest control and force a sale of BP's stake to a state-controlled Gazprom or Rosneft.

''This is just a return to the corporate-raiding activities that were prevalent in Russia in the 1990s," Peter Sutherland, BP's chairman, said in Sweden last week.

Gazprom has seized majority stake in a number of foreign-controlled energy projects in Russia following potentially crippling investigations by state agencies.

While several business leaders who made it big had either lost control of their businesses during Vladimir Putin's eight years as president of Russia, all of BP's partners prospered during the Putin years.

Agents of the FSB, the Russian security agency, had raided TNK-BP as part of an investigation in which a senior manager was arrested on charges of industrial espionage.

Tax investigators who had also swooped on the company had also questioned Dudley at length.

BP alleged that Russian security guards had prevented some of its employees from entering TNK-BP's Moscow headquarters.

While neither side has a controlling stake, tax investigations by government agencies and visa problems for foreign employees made chairman Dudley accuse the Russian partners of trying to create problems for the company.

The Russians partners in turn demanded Dudley's dismissal.

Putin, now Russia's prime minister, blame the conflict on the 50-50 stake formula.

The Russians want TNK-BP to hire own managers. They also want equal representation on the board.