Gordon Brown is poised to intervene in the battle over TNK-BP next week by appealing directly to President Medvedev for help in defusing the row.

The Prime Minister is scheduled to meet the new Russian leader for the first time on Monday at the G8 summit in Hokkaido, Japan. The leaders are expected to hold brief bilateral talks on the sidelines of the summit and TNK-BP is one of several issues likely to come up, sources said.

The meeting comes after the dispute over control of TNK-BP escalated further yesterday when it emerged that Robert Dudley, chief executive of the venture, could be forced to leave Russia within weeks over a row about visas.

Two expatriate workers were forced to leave yesterday for the same reason, according to a BP spokesman.

Top foreign executives at TNK-BP, including James Owen, chief finance officer, and Timothy Summers, chief operating officer, were also under threat after a steep cut in the number of foreign specialists allowed to work for TNK-BP. Nearly 100 staff have been affected by the visa row.

Mr Dudley said: “We have been given no ground to believe this issue will be resolved before senior international staff and their families will have to leave Russia.” He predicted that they would have to leave this month.

The forced departure of Mr Dudley and his colleagues, which would leave operational control in the hands of TNK-BP's 50 per cent Russian co-investors, represents the latest salvo in a sustained attack on BP in Russia. TNK-BP has been the subject of raids by security agents and last month

Mr Dudley was hauled in front of prosecutors in Moscow for five hours of questioning.

A Downing Street spokesman declined to comment on the detail of the talks. A spokesman for the British Embassy in Moscow said that the leaders would have a wide-ranging talk, including on what he described as British investments in Russia.

TNK-BP is the largest British investment in Russia and one of the largest of all foreign investments in the country.

BP also declined to comment, but sources close to the oil group expected TNK-BP to be discussed.

BP has close ties to the Brown administration. TNK-BP's deputy chairman is Lord Robertson of Port Ellen, the former Defence Secretary and Nato Secretary-General who also served as chairman of the Scottish Labour Party.

Peter Mandelson, the European Trade Commissioner, and Benita Ferrero-Waldner, the External Relations Commissioner, have put pressure on the Russian Government in an attempt to settle the dispute. Mr Mandelson accused the company's Russian shareholders of “menacing behaviour”.

TNK-BP was created in 2003 when BP struck a partnership deal with four Russian billionaires - Viktor Vekselberg, Mikhail Fridman, German Khan and Len Blavatnik. That partnership has since broken down.

Good relations between Moscow and London established after Vladimir Putin came to power in 2000 deteriorated after Russia accused Britain of hosting enemies of the Kremlin.

The murder of Alexander Litvinenko prompted tit-for-tat diplomatic expulsions. Nevertheless, Britain was the biggest foreign investor in Russia last year.

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