The statement suggested that Prime Minister Gordon Brown's government is trying to disavow a claim by a security agent that there are "very strong indications that it was a state action," The Telegraph reported.
Litvinenko was poisoned in London in 2006 and died several weeks later. Before his death, he blamed then-President Vladimir Putin.
Russia has refused the extradition of Andrei Luguvoi, also a former KGB agent, who is the only named suspect in the case.
Brown met with Russian President Dmitry Medvedev on the sidelines of the Group of Eight summit in Japan.
"I made it clear to President Medvedev that the Litvinenko issue would not be closed," Brown said later. "We have justice to do on the part of someone who was murdered on British soil and it is not an acceptable position to be where we are."