Andrei Lugovoy said Thursday, the one-year anniversary of Litvinenko's death from radioactive polonium-210, that he did not poison the spy-turned-dissident during their meeting at a London hotel in November 2006, The Times of London reported Friday.

Lugovoy and his business partner Dmitri Kovtun said at their Moscow news conference that Litvinenko may have operated within the nuclear black market at the behest of MI6, the British secret service. The two men met with Litvinenko shortly before his death at London's Millennium Hotel.

Kovtun said doctors have discovered “a rather large amount of polonium” in his body. He said Litvinenko's death and his condition may have been accidental.

“It’s perfectly possible that his death was just an unfortunate accident -- and Britain’s MI6 intelligence service found itself in a ridiculous situation,” Kovtun told The Times.

Lugovoy elaborated on the theory.

“This is a serious possibility that needs checking," he said at the news conference. "What if Litvinenko grew careless with polonium? How was his former boss (in MI6) supposed to explain his death?”