Russia's Foreign Minister warned against a "politicisation" of the Litvinenko affair as British police arrived in Moscow to pursue their investigation into the poisoning of the former Russian intelligence officer in London.
Sergei Lavrov launched a thinly veiled attack on the cabinet minister Peter Hain, warning that Anglo-Russian relations were being damaged by the fallout from the death of Alexander Litvinenko. Last week, Mr Hain, the Northern Ireland Secretary, urged Vladimir Putin to "retake" the democratic road, and spoke of "extremely murky murders" that had "clouded" the Russian President's time in the Kremlin.
Mr Lavrov, who was visiting Brussels on the sidelines of a meeting of the Organisation for Security and Co-operation in Europe, urged British politicians to refrain from speculation until the full truth is known.
The Foreign Minister said he had spoken to his counterpart, Margaret Beckett, to impress upon her the need to keep politics out of what is a police investigation. "For official representatives to fan this campaign [suggesting the Kremlin may have been involved in Mr Litvinenko's death] is unacceptable," Mr Lavrov said. "It will damage our relations. There is a need to avoid the politicisation of this ... tragedy. There is a need to avoid speculation."
He also denied reports that Russia has lodged an official complaint with the Government about the release of Mr Litvinenko's dramatic deathbed letter in which the former spy accused Mr Putin of personally ordering his murder.
A British embassy spokesman in Moscow said the investigative team from Scotland Yard would remain there "for as long as is necessary" and was "keen to find out as much as possible".
Lawyers for the former Russian security officer Mikhail Trepashkin, who is in jail for revealing state secrets, said their client was anxious to be interviewed by the British detectives because he had important information. Mr Trepashkin knew Mr Litvinenko and apparently warned him several years ago about a government-sponsored death squad that intended to kill him and other opponents.
His lawyer, Yelena Lipt-ser, said Mr Trepashkin suffered from asthma and was not receiving adequate treatment for it in prison. "His life is in danger and he may die any night of asthma," she said.
John Reid, the Home Secretary, insisted that the quantities of polonium-210 discovered by the British authorities were minuscule, and played down fears of a diplomatic rupture with the Russians.
After briefing European interior ministers in Brussels on the investigation, Mr Reid said that, while one millionth of a gram of the substance could be fatal, "the sort of traces we are finding are no more than one millionth of a millionth of a gram. There is no reason for undue concern".
Traces of the substance have been found on several planes, including two which flew between London and Moscow. The Home Secretary admitted that it is not likely that the authorities will be able to trace the origin of the radioactive material from the samples from Mr Litvinenko's body.
He said test results from 68 people who might have been in contact with the material found on the planes or with Mr Litvinenko, including family and hospital staff, had shown "negligible" traces of radioactivity.
British health officials have been in contact with European counterparts as the inquiry into Mr Litvinenko's death takes on an international dimension.
Mario Scaramella, the Italian contact who set up the appointment in a London sushi bar where Mr Litvinenko may have been poisoned, repeated his claim that he too had received a heavy dose of polonium-210. "I have five times the fatal dose of polonium-210 in my body," he told Italian television news.
A spokesperson for University College Hospital in London, where Mr Scaramella he is under observation, said the 36-year-old Italian was well. Mr Reid said Mr Scaramella was showing "much lower" levels of the radioactive substance than that blamed for Mr Litvinenko's death.
Mr Scaramella has been widely attacked in the Italian media because transcripts of phone conversations he had with a supporter of the former prime minister Silvio Berlusconi in the Senate allegedly disclosed the two men discussing ways of smearing Romano Prodi as a tool of the Russians.
But now, in a three-page e-mail sent to his lawyer in Rome, the self-styled professor from Naples warns that he has ways of defending himself.
He claims to have documents and filmed evidence "to rebut all the accusations that have wrongfully and dangerously been made against me".
He also claims to have "a lot of information on politicians and journalists relating to Soviet espionage".
Only the generalities in the e-mail were released to the press: detailed allegations relating to organisations including the United Nations and the Italian embassy in London were kept secret.
In the letter, Mr Scaramella suggested that he and Mr Litvinenko had been poisoned on account of "the information that Mr Litvinenko had been transmitting to me for months".
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