Russia today accused Britain of politicising the case of murdered Kremlin critic Alexander Litvinenko and said the affair was hurting the two countries' relations.
"We see attempts from the British side to use the criminal case to build up some sort of political campaign," said Russian Foreign Minister Sergei Lavrov. "We are against that. It is the business of the law enforcement agencies."
Asked if the affair was having a negative impact on Russia's relationship with Britain, Mr Lavrov said: "Such an effect is being felt."
British prosecutors have named Andrei Lugovoy, a business contact of Mr Litvinenko's, as their chief suspect in his murder and asked Russia to extradite him. But Moscow has refused, saying it cannot extradite its own citizens.
Britain's foreign ministry was quick to counter Mr Lavrov's comments, saying the case was purely a criminal matter.
British Prime Minister Tony Blair and Russian President Vladimir Putin are to meet in the German resort of Heiligendamm next week at the Group of Eight summit. It is not clear if they would have a separate, face-to-face meeting.
Mr Litvinenko, a former officer in Russia's Federal Security Service who took British citizenship, died last year in a London hospital after being poisoned by the radioactive isotope polonium 210.
Mr Litvinenko said in a deathbed statement he believed the Kremlin was behind his murder.