The Russian foreign minister said on the final day of the inquiry in London that Moscow's fears that the probe would be biased and non-transparent appeared justified.
"In August 2014, the Investigative Committee was forced to forego participation in the public inquiry. It is solely related to the fact that contrary to its name, it is not transparent either for the Russian side or the public," said the foreign ministry.
"Thus there were serious concerns related to its possible politicisation. In the end our concerns were fully justified," it said in a statement.
Moscow also took issue with the fact that Britain tried to question Dmitry Kovtun, one of the two suspects in Litvinenko's murder, by video link, saying that such testimony would contravene Russian law and bilateral accords with Britain.
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President Vladimir Putin's spokesman separately told reporters that Russian officials did not set much store by the probe.
"No, we do not trust (the inquiry)," spokesman Dmitry Peskov told reporters, declining to comment on the future of the investigation.
Kovtun and a second Russian, Andrei Lugovoi, are wanted by British police for allegedly poisoning Kremlin critic Litvinenko at London's Millennium Hotel in November 2006 using tea laced with the radioactive isotope polonium-210.
In a letter dictated from his deathbed Litvinenko, who was a former officer with the Russian security service the FSB, accused Putin of having ordered his murder.