"We cannot grant a visa to Mr Dudley before he presents a valid contract. The previous contract expired and we have no proof that it has been prolonged," Konstantin Poltoranin, a spokesman at the Federal Migration Service (FMS), told Reuters.

Dudley's contract expired last year but BP says it is still valid under Russian law because it has never been officially terminated and as a result rolls over automatically.

Mikhail Fridman, Lev Blavatnik, Viktor Vekselberg and German Khan, TNK-BP's four Russian billionaire co-owners, who want to sack Dudley as part of their dispute with BP over the company's strategy and management control, say the contract has never been officially renewed and is therefore no longer valid.

A source close to TNK-BP dismissed as "nonsense" the idea that Dudley did not have a valid contract, saying a board resolution tabled by the Russian oligarchs to sack Dudley earlier this year in itself proved that they recognised his contact was valid.

Dudley has a valid Russian work permit but needs to present a valid work contract to get his visa renewed. His visa expired on 19 July, but the migration service agreed to give him a transit visa, which is valid until 27 July.

"He (Dudley) has been given 10 days to present a contract. We may extend his visa one more time, but without a valid contract, he cannot work in Russia," the FMS's Poltoranin said.

Dudley is also facing penalties from a judge after a labour inspector found some minor violations, the TNK-BP source said. These could include suspending him from his post for a period of up to three years.

"Obviously the pressure is mounting," the source said. "The likelihood is that somehow they will try to engineer Dudley's suspension this week so that the Migration Service can then say they don't need to consider his visa request and he has to leave."

"It's ridiculous but this is the reality."

Published: 21 July 2008 08:13 GMT  | Last updated: 21 July 2008 09:35 GMT