Did murdered ex-spy Litvinenko work for British intelligence?

The case of Alexander Litvinenko, who was poisoned with a lethal dose of radioactive polonium-210 in a London bar a year ago, just keeps getting murkier.

Last weekend, the London-based Daily Mail, citing anonymous intelligence and diplomatic sources, reported that the former KGB agent was also an agent of Britain's MI6 spy agency who received a monthly retainer of $4,000.

"It is understood that Sir John Scarlett, now the head of MI6 and once based in Moscow, was involved in recruiting him to the Secret Intelligence Service," the paper said. "The fact that the 43-year-old ex-Russian spy was actually working for Britain when he died could provide the key to his extraordinary killing."

His widow, Marina Litvinenko, has denied the allegation, insisting that her husband "was not the kind of person who would be useful to the British security services."

But in Russia, Andrei Lugovoi, the ex-KGB agent accused by the British government of murdering Mr. Litvinenko, declared that he has been vindicated.

"I hope the British public will demand after this publication in the newspaper that their secret services shed light on the situation surrounding Litvinenko's death," a jubilant Mr. Lugovoi, who is currently running for parliament on the ultranationalist Liberal Democratic Party ticket, told the official ITAR-Tass agency.

Lugovoi has claimed in the past that Litvinenko and his sponsor, exiled anti-Kremlin tycoon Boris Berezovsky, were both agents of MI6. He has hinted that Litvinenko was actually killed by British intelligence as part of a dark plot to slander Putin and wreck Russia's relations with the West. Lugovoi further claimed that Mr. Berezovsky and Litvinenko had tried to recruit him for anti-Kremlin activities.

"This new information [from the Daily Mail] confirms what Lugovoi has been saying," says Lugovoi's lawyer, Andrei Romashov. "People [in the West] have refused to believe him just because he's a Russian."

Litvinenko died two weeks after he took tea in a London bar with two other ex-KGB agents last November. An autopsy linked his death to exposure from polonium-210, a rare nuclear substance produced mainly in Russia.

The other two men, Lugovoi and Dmitri Kovtun, turned up in Moscow, also showing signs of radiation poisoning, after spreading an apparently inadvertent trail of polonium dust halfway around Europe.

Many in the West suspected that Russian secret services may have murdered Litvinenko in revenge for his defection, perhaps with Kremlin approval. The British government decried the act of "nuclear terrorism" in the heart of London, and a diplomatic storm ensued.

Last May, Britain officially charged Lugovoi with the crime, and demanded his extradition. Mr. Putin personally expressed Moscow's refusal, but said Russia would conduct its own investigation. Last week, Russia's chief prosecutor complained that his probe into the affair was stalled due to "lack of cooperation" from Britain. In July, Britain expelled four Russian diplomats to underscore its anger over Moscow's refusal to turn over Lugovoi. Russia replied by kicking out four British diplomats, and many experts predicted the affair might quietly peter out. That seems unlikely now.

Some experts caution that the Daily Mail story may not be entirely accurate.

"We know that a lot of things appear in the British media that are not solid information," says Masha Lipman, an expert with the Carnegie Center in Moscow. "Who's working for a spy agency is not something that can be easily confirmed."

But Lugovoi's vocal supporters, who are widespread in Russia's media and political establishment, say his narrative has been borne out.

"Litvinenko's death was used as a pretext to begin a political provocation against Russia, to damage Russia's image," says Viktor Alksnis, a nationalist deputy of the State Duma. "The whole story smells bad."