TNK-BP, the private Russian oil company that is set to be nationalised, is making a fresh attempt to prevent the publication of papers a former employee claims provide evidence of high-level corporate and government corruption.

The gagging order, lifted by a British judge last week but still in place while the company seeks permission to appeal, is part of a dispute dating back to March this year between Russia's third largest oil company and Igor Lazurenko.

Lazurenko, who resigned as TNK-BP's head of new business, development and processing in April, is accused of fraud by his former employer.

Last week, the Chancellor of London's High Court, Andrew Morritt, lifted an injunction that has been in place since July, saying the argument in favour of gagging was based on a Russian employment contract, and as such was a matter for Russian law.

Lawyers for the company have asked for permission to appeal, and court officials have opened a window to consider whether to grant a hearing between Dec. 13 and Jan. 3.

Lawyers for both sides were not responding to requests for comment on Tuesday, but Morritt's ruling on Oct. 16 revealed that Lazurenko is naming Transneft, the Russian pipelines monopoly, in his corruption allegations.

News the case could drag on comes a day after the owners of Russia's third largest oil company, British oil group BP and the Russian AAR consortium, agreed on Monday to a $55 billion sale of TNK-BP to state-controlled Rosneft.

BP, set to get a near 20 percent stake in Rosneft as part-payment, has called the deal a "heads of agreement" that is contingent on government permissions and other discussions.

Rosneft is controlled by the Russian government and headed by Igor Sechin, a close ally of President Vladimir Putin and Rusia's most powerful energy industry official.

Lazurenko still faces allegations of fraud brought against him by his former employer.

In March, TNK-BP director and shareholder German Khan made Lazurenko the subject of an internal inquiry into the propriety of the alleged receipt of certain substantial payments.

Lazurenko, who had been an employee since 2003, resigned the following month. According to the Oct. 16 court papers, he approached TNK-BP's lawyers in June and showed them the documents, saying he considered they "would be damaging to TNK-BP if disclosed because they purport to reveal high-level personnel engaging in corrupt behaviour."

A later witness statement by Lazurenko, also revealed in the Oct. 16 papers, said the documents contained "details of wrongdoing between TNK-BP and companies beneficially owned and controlled by the most senior officers of Transneft and officials of the Ministry of Energy responsible for regulating and monitoring the oil industry in Russia."

TNK-BP has denied any wrongdoing and says it continues to believe in the merits of the injunction. Its representatives in London said they had nothing to add on Tuesday.

Transneft had no immediate comment.