A doubling of the returns from its troubled Russian joint venture and the soaring cost of oil helped BP to report record second-quarter profits of $9.46 billion (£4.74 billion).

The result, a 28 per cent improvement on the previous year, cast fresh light on the importance of TNK-BP to the British oil giant. BP's share of net profits from the venture surged to $1.35 billion, from $686 million, and represents 14 per cent of total group income. At 919 million barrels of oil equivalent a day, BP's share of the venture's output represents a quarter of the British group's total production.

Tony Hayward, chief executive of BP, said: “In many respects TNK-BP is having its best year ever.” He reiterated BP's determination to fight with every weapon at its disposal to maintain its grip on TNK-BP. “The other shareholders want to tear up the agreement they willingly signed in 2003. We are not prepared to do that and will vigorously defend our rights,” he continued. “It's unacceptable to have one set of rules in Russia and another set of rules internationally.”

The result came as the whereabouts of Bob Dudley, chief executive of TNK-BP, remained unclear. Mr Hayward said that Mr Dudley, who was forced to leave Moscow last Thursday, was somewhere in Central Europe, taking a break from what was described as weeks of intimidation at the hands of AAP, BP's partner in the Russian venture.

Despite the continuing concern over the situation at TNK-BP, analysts responded positively to the results. Richard Griffith, director of equity research at Evolution Securities, said: “The turnaround in the business is there. Tony Hayward is meeting the objectives he set out last year.”

The bulk of gains were derived from BP's exploration and production division, which benefited from higher oil and gas prices during the period. Oil averaged more than $120 a barrel during the quarter, nearly twice the level of 2007. Crude touched a record high of $147 per barrel on July 11, only a few days after the end of the quarter.

Although production remained stable at 3.83million barrels per day, BP said that it was on track to restore full production from its Thunder Horse platform in the Gulf of Mexico, the world's largest deep-water rig, by the end of the year.

The company also reported an improvement in volumes at its troubled refining operation. Refinery throughput increased to 2.239 million barrels per day, up from 2.128 million a year ago, reflecting continued efforts to resolve safety and technical problems at its American facilities at Texas City and Whiting, Indiana.

However, BP said that profits from refining and marketing had plunged to $539 million during the second quarter, down from $2.7 billion a year ago.

The company blamed the result on poor margins, which it said remained significantly lower than in 2007, as well as lower sales volumes resulting from higher fuel prices and lower demand. Average global refining margins, at $8.19 per barrel for the quarter, were less than half the $16.66 reported a year ago.

Mr Hayward also hinted at further job cuts, despite a swath of losses over the past year. “Our costs have become uncompetitive. This is a major opportunity for improvement and we are grasping it with both hands."

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