MOSCOW — BP, the huge British oil company, on Friday rejected demands from a group of Russian billionaires to fire the head of the lucrative TNK-BP natural gas venture, deepening a confrontation between shareholders as the country’s biggest state-controlled oil companies seek a stake in the venture.

Tensions between Russian and foreign shareholders of TNK-BP, the largest foreign oil producer in Russia, boiled over this week after the billionaires’ consortium sought the resignation of the TNK-BP chief executive, Robert Dudley.

The investors — Mikhail Fridman, Viktor Vekselberg and Len Blavatnik, a Russian-born American citizen — cited disagreements over investments and asset sales, and expressed concern that Mr. Dudley was managing the venture solely in BP’s interests.

On Friday, BP said Mr. Dudley was not stepping down. “We’re standing very firmly behind him,” a spokesman for BP in London, Roddy Kennedy, said.

This week, Mr. Dudley, who has led the joint venture since its formation in 2003, lashed out at the Russian shareholders, telling a Russian newspaper that the company was suffering from a “breakdown” in management, a remark that the consortium called “deeply inappropriate.”

The billionaires refused to attend a meeting Thursday of the company’s board in Cyprus because Mr. Dudley had not been removed. Vladimir Buyanov, BP’s spokesman in Moscow, said that Mr. Fridman, Mr. Vekselberg and Mr. Blavatnik instead met in Cyprus with the chairman of BP, Anthony B. Hayward.

“I can say both groups made proposals regarding management of the company,” Mr. Buyanov said. He declined to reveal any details of the meeting or to comment on the demands to fire Mr. Dudley.

BP and AlfaAccessRenova, the collective name for the investment vehicles representing the billionaires’ interests, each own 50 percent of TNK-BP. The company accounts for about a quarter of BP’s total worldwide production. As oil prices have soared, the Kremlin has backtracked on profit-sharing deals. Gazprom, the Russian national gas behemoth, has long been positioning itself to take a potentially major stake in TNK-BP.

Since Vladimir V. Putin, then president of Russia and now the prime minister, and Tony Blair, then the British prime minister, created TNK-BP with an $8 billion investment, several major oil companies operating in Russia have fallen into difficulty.

Yukos, once the biggest private company in Russia, was dismantled in 2003 after prosecutors sent its former chief, Mikhail Khodorkovsky, to a Siberian prison for tax evasion. The state company Rosneft later acquired most of the Yukos assets. In 2006,Royal Dutch Shell was pressured into selling a controlling stake in its $20 billion Sakhalin-2 oil project to Gazprom at a below-market price after environmental regulators threatened it with billions of dollars in fines.

Last June, BP ceded to Gazprom its stake in the oil-rich Kovykta field, a Siberian deposit with enough natural gas to supply Asia for five years, a move that came as Mr. Putin sought to end foreign ownership of Russia’s biggest energy assets.

More recently, Russian authorities raided the Moscow offices of BP and TNK-BP, accusing a TNK-BP employee of industrial espionage and opening an investigation into tax evasion and possible environmental violations.

A week later, BP’s troubles in Russia continued as the authorities questioned the legality of work permits for the company’s expatriate employees.

The dispute among TNK-BP shareholders is expected to be a test of the position on foreign investment in Russia of the newly inaugurated president, Dmitri Medvedev.