Attempts to oust BP from Russia have taken a sinister, official twist, as the Russian authorities ordered the refusal of work permits for overseas executives in the TNK-BP joint venture.

The initiative by the Moscow city authorities could see the barring from the country within the month of Robert Dudley, the American BP executive who heads TNK-BP - a move which would herald the beginning of the end for the venture and BP's Russian ambitions.

The current status of BP's senior people in Russia is that their current visas run out at the end of the month and unless they are granted new work permits soon they will have to leave the country.

Fewer than half the permits that have been applied for have been approved, and the application process for the remaining new visas is expected to get bound up in red tape in the coming weeks.

"We're all out of here at the latest by the end of July," an unnamed TNK-BP executive was reported as saying. "With all the best will in the world, there is no time."

The move is believed to have been orchestrated by Viktor Vekselberg, one of four oligarchs who co-own TNK-BP, the giant Russian oil producer built by former BP chief executive Lord Brown.

The visa impasse is widely seen as hastening the denouement to a breakup of TNK-BP after weeks of harrassment which has seen Dudley and his fellow executives variously accused of tax evasion and breaches of labour relations and health and safety laws.

BP has been forthright in its condemnation of the campaign by the oligarchs calling it a return to the corporate raiding seen in Russia of the early 1990s.