Mr Litvinenko, 43, died in London after being poisoned
Justice campaigners say they are disappointed at the lack of progress made in the case of murdered Russian dissident Alexander Litvinenko.
On the second anniversary of his death, the Litvinenko Justice Foundation again called for the extradition of prime suspect Andrei Lugovoi, 42.
Former KGB agent Mr Litvinenko, 43, died on 23 November 2006 in London after being poisoned with Polonium-210.
The UK suspects fellow former agent Mr Lugovoi of murder, which he denies.
Mr Litvinenko fell ill shortly after drinking tea during a meeting at a West End hotel with former contacts Mr Lugovoi and Dmitri Kovtun.
The Russian government denies any involvement in his death and has asserted Mr Lugovoi was framed by MI6.
In May 2007, the Crown Prosecution Service formally submitted an extradition request to Moscow for Mr Lugovoi to stand trial in the UK.
This remains current, but Russia has so far refused to co-operate, saying it would be against its constitution to do so.
Mr Litvinenko's widow, Marina, has since met British and US government officials in a bid for help but little progress has been made.
She is marking the second anniversary of her husband's death privately.
But the justice foundation, of which she is a founder member, expressed its disappointment in a statement.
It read: "There has been no progress regarding the extradition to the UK of the prime suspect, Andrei Lugovoi, from the Russian Federation.
"While there is a general consensus that the Russian state was involved, the official line of 'treating it as a common crime' remains in force.
"All evidence collected by the police, including scientific data related to the origins of radioactive Polonium-210, remain classified."
The statement said Mrs Litvinenko's direct appeal to current Russian president Dmitry Medvedev to stop protecting Mr Lugovoi had met no response.
It said her request for a "full and open inquest" was still being considered by the coroner after seven months.
Alex Goldfarb, an associate of Litvinenko and author of a book about his killing, said he was "very disappointed" the case was not developing.
He told BBC News: "We have been campaigning for the government to recognise this was a state-sponsored terrorist attack, but unfortunately the official line continues to be that it was just a normal crime.
"In essence the situation is in stalemate. It is frustrating for family and friends."
A spokeswoman for Scotland Yard said she could not comment on the case.