LONDON - Britain's relations with Russia have been thrown into crisis as the Moscow authorities said they would refuse to hand over the man accused of murdering the former KGB officer, Alexander Litvinenko, in London last November.
Andrei Lugovoy, who met Mr Litvinenko on the day he was poisoned with the rare radioactive substance, polonium 210, has denied murder, claiming that the accusations are politically motivated.
"I did not kill Litvinenko, I have no relation to his death and I can only express well-founded distrust for the so-called basis of proof collected by British judicial officials," he said.
But the Director of Public Prosecutions, Sir Ken McDonald, announced that the Metropolitan police have sufficient evidence to charge Mr Lugovoy, with the "deliberate poisoning".
His announcement was backed up by the Attorney General, Lord Goldsmith, who confirmed that the UK government would immediately seek Mr Lugovoy's extradition.
The Russian ambassador, Yuri Fedotov, was called to the Foreign Office to be told by the Foreign Secretary, Margaret Beckett, that the UK expected Russia's "full co-operation".
But Russia's Prosecutor General's Office has said that any Russian accused of Litvinenko's death should be tried in Russia.
"A citizen of the Russian Federation cannot be extradited to another state. A citizen who has committed a crime on the territory of a foreign country can be held criminally responsible, but only on Russian territory," Marina Gridneva, of the federal Prosecutor General's Office said.
Relations between Russia and the UK had been strained since the British refused to extradite the former Russian tycoon, Boris Berezovsky, and the Chechen leader, Akhmed Zakayev, who have both sought asylum in the UK after falling foul of President Vladimir Putin's government.
British judges ruled that neither man was likely to get a fair trial in Russia.
Russian dissidents in this country claim that the Kremlin is protecting Litvinenko's killers because - they suspect - the Russian secret service, the FSB, and possibly the president himself are implicated.
Mr Litvinenko, who was 46 when he died, had served as officer in the KGB and its successor organisation, the FSB.
He broke with them in 1998, when Mr Putin was FSB head, and accused his former employers of plotting to murder Berezovsky, who was using his wealth to fund civil rights groups.
Having fled abroad and gained British citizenship, Mr Litvinenko went on to accuse the FSB of being involved in terrorist atrocities that were then attributed to Chechen separatists, to justify the war Mr Putin was waging in Chechenya.
At the time of his death, Litvinenko was investigating the murder of the journalist, Anna Politovskaya, another prominent critic of Russia's treatment of the Chechens.
He fell ill on November 1, after meeting Mr Lugovoy and two other Russians for tea at the Millennium Hotel, in central London.
Three weeks later, Mr Litvinenko died a protracted, painful death in an intensive care unit in London.
His hair fell out, his skin turned yellow, and his organs failed as the isotope poisoning took effect.
He left a message accusing President Putin of ordering his murder.
Russian government spokesmen have dismissed the accusation, claiming that Litvinenko was not an important figure.
The manner of his death prompted hundreds of people to ring emergency lines, fearing that they had symptoms of polonium poisoning.
Police also uncovered a plutonium trail which made them suspect that the substance had been smuggled into the UK by Mr Lugovoy or by another Russian businessman, Dmitri Kovtun, who also met Mr Litvinenko at the Millennium Hotel.
Traces of the substance were found at the Millenium Hotel, at two other London hotels where Mr Lugovoy had stayed, on three aircraft that had been flown between London and Moscow, and even in the Emirates Stadium, where Mr Lugovoy went to watch a match between Arsenal and CSKA Moscow.
Scotland Yard detectives went to Moscow to speak to both men.
They claimed to be victims of poisoning rather than poisoners.
Mr Litvinenko's widow, Marina, yesterday praised the Scotland Yard detectives handling case.
She added: "It is important to me that my husband didn't die in vain and that the perpetrators of his murder are brought to justice in the UK. I want my son to know that my husband's death is not just for nothing."
She also revealed that the Russian ambassador had asked to see her and had conceded that the affair was damaging Russia's interests.
"I suggested to the ambassador the best way to restore Russia's reputation would be to co-operate fully with the extradition request," she told the BBC.
The exiled Chechen leader, Akhmed Zakayev, said: "Alexander Litvinenko and I were close friends and neighbours. His brutal murder was a terrible tragedy. I hope the announcement today will result in Sasha's killer being brought to justice."
- INDEPENDENTBy Andy McSmith