The suggestion came during a BBC This World film, called "Britain's Most Wanted," by Mark Franchetti, which was shown on Sunday.
"Several people I interviewed, including a former KGB general, believe that if [Andrei] Lugovoi did take part in Litvinenko's murder, he was used without knowing it," Franchetti said. "It is possible, experts in covert operations say, that he was tricked into believing that the substance used against Litvinenko was a truth serum, or some debilitating drug."
Lugovoi, a former Kremlin bodyguard, dismissed the claim on Monday: "I am not a small naive boy, I am too professional, including in terms of security, to be unaware of being used by someone."
He said "this version is absurd as far as common sense goes, but politically is good enough for British intelligence and the true murderers."
Britain's Scotland Yard has stated that Lugovoi poisoned Litvinenko by adding a dose of polonium-210 to his tea during a meeting in London in 2006. Lugovoi has strenuously denied any involvement in frequent interviews.
Lugovoi said on the BBC program that Litvinenko's murder, the first known case of radioactive substances being used in an assassination, was part of a nefarious and well-thought out plot that involved Britain's intelligence services and opponents of Russian President Vladimir Putin.
"MI6 wanted to kill him in order to discredit Russia's government, because now in the West they all say that Litvinenko was killed on Kremlin and FSB orders," he claimed.
Litvinenko was the co-author of a book that claimed that one-time colleagues in Russia's Federal Security Service were responsible for deadly apartment bombings in Russia in 1999. The ex-KGB man arrived in Britain in 2000 and was later granted political asylum.
The murder of the Kremlin critic Litvinenko subsequently led to the worst diplomatic crisis between Britain and Russia since the end of the Cold War, with the two countries engaging in tit-for-tat diplomatic expulsions in July.
Moscow has refused to extradite Lugovoi to Britain, citing its Constitution, which bars citizens from being extradited for trial abroad, offering instead to try Lugovoi in Russia if sufficient evidence is provided.
In September, Lugovoi confirmed that he would run for parliament as a candidate for the Liberal Democratic Party, led by outspoken pro-Kremlin ultranationalist Vladimir Zhirinovsky. Under Russian law, a seat in the State Duma would give Lugovoi immunity from prosecution.