BP’s grip on its Russian oil joint venture was slipping on Monday after authorities in Moscow refused work permits to many of the company’s foreign executives in a ruling that could see all of them forced out of the country by the end of the month.

The ruling is the latest twist in anacrimonious struggle between BP and its Russian partners over control of the TNK-BP joint venture. It means Robert Dudley, the BP-backed chief executive of the joint venture, along with its chief financial officer and a number of other executives will have to leave Russia unless they can secure visas rapidly. Their departure would leave operational control of the company in the hands of their Russian partners.