Andrei Lugovoy told a news conference he had evidence to back up his claim but would only give details to Russian investigators. Lugovoy, a former KGB agent, met with Litvinenko in London hours before he fell ill in November.
Britain has requested Lugovoy’s extradition to face murder charges. Russia refuses to hand him over.
Lugovoy described the British accusations as an attempt to divert attention from Litvinenko’s contacts with Britain’s spy services.
He said Litvinenko had tried to recruit him to work for MI6 and gather compromising materials about Russian President Vladimir Putin, but that he refused.
“It’s hard to get rid of the thought that Litvinenko was an agent who got out of the secret service’s control and was eliminated,” Said Lugovoy. “Even if it was not done by the secret service itself, it was done under its control.”
The Foreign Office declined comment.
Oleg Gordievsky, a former top KGB spy who worked for MI6 and defected to Britain, dismissed Lugovoy’s claims as “silly fantasies”.
He said Litvinenko had worked for a domestic intelligence agency in Russia and was of no interest to British intelligence.
Litvinenko died on November 23 in a London hospital after ingesting radioactive polonium-210.
In a deathbed statement, he accused Putin of being behind his killing.
Lugovoy claimed British security services were unhappy with Litvinenko for boasting of his contacts with senior MI6 officials and spilling secrets.
“In conversations with me, Litvinenko often went beyond his role as a recruitment agent and told me many things he shouldn’t have said,” said Lugovoy. “I got an impression that he was really getting out of British secret services’ control. He believed that the British paid him too little for his service.”