Russia asked Britain to extradite former Russneft owner Mikhail Gutseriyev, who is accused of tax evasion, an Interior Ministry official said Monday.

The announcement came on the same day that Britain's new ambassador, Anne Pringle, took her post in Moscow, following a series of extradition wrangles that severely frayed bilateral ties.

"He is in England. A request for his extradition has been sent," Igor Tsokolov, head of the ministry's department that investigates organized economic crime, said of Gutseriyev, RIA-Novosti reported.

Gutseriyev, the former chief of the country's seventh-largest oil producer, fled Russia last year, saying the accusations against him were false. Russia issued an international arrest warrant for the businessman after he failed to appear for questioning.

A company affiliated with billionaire Oleg Deripaska's Basic Element requested permission to buy Russneft in July 2007. The Federal Anti-Monopoly Service has delayed approval because of numerous lawsuits brought against the oil firm by the Federal Tax Service.

The British Embassy declined to comment. "We neither confirm nor deny extradition requests," an embassy representative said on customary condition of anonymity. Ties with Britain deteriorated after British courts consistently refused to extradite a number of other prominent businessmen and political figures, including Boris Berezovsky and Chechen separatist Akhmed Zakayev. The situation worsened after Russia ruled out extradition of Andrei Lugovoi, whom British prosecutors named as the prime suspect in the radioactive poisoning of former security services officer Alexander Litvinenko.

Acting on an extradition request, British police will arrest the person in question and take him to court, said Peter Caldwell, an extradition lawyer in London. The court may then release the person on bail.

"In respect to requests from Russia, the lawyer must explain ... whatever the person did wrong," Caldwell said. "It's not necessary to provide evidence amounting to proof, but the conduct must be for what would be an offense in both Russia and in the U.K."

Extradition to Russia could take six months or more, he said. "The experience of the court in Russian cases is that arguments are made about whether the defendant can have a fair trial," he said.

The request showed that Russia was ready for another war of words with Britain, despite hopes for a better future voiced by then-Ambassador Tony Brenton last month. "My advice to my ... successor will be: There is enough good there ... to help build the relationship in a positive direction," Brenton said in an interview with The Moscow Times.

A career diplomat, Pringle worked at the British Embassy in Moscow during the early 1980s and later served as ambassador to the Czech Republic.

Pringle's husband, lawyer Bleddyn Phillips, has joined Clifford Chance's office in Moscow, where he will continue serving as global head of the firm's oil and gas practice, spokeswoman Yelena Belousova said Monday.

Staff Writer Anna Malpas contributed to this report.