Russia's Foreign Minister has accused Britain of using the case of murdered Kremlin critic Alexander Litvinenko in a political campaign, which is harming ties between the two countries.
Mr Litvinenko, a former spy, died last year in a London hospital after being poisoned by the radioactive substance polonium-210.
Russian minister Sergei Lavrov said the British were using the criminal case to 'stir up some kind of political campaign'.
However the British Foreign Office has denied any attempt to politicise the issue, noting it was being dealt with by 'the relevant organs in the UK'.
Britain is seeking the extradition of Russian former spy Andrei Lugovoi in connection with the murder of Mr Litvinenko.
Russia has so far refused to extradite him.
