In a retaliatory move, Britain said Monday it will expel four Russian diplomats from their embassy in London because Russia has refused to hand over Andrei Lugovoi, the main murder suspect in the London poisoning case of a former KGB spy.

"The Russian government has failed to register either how seriously we treat this case or the seriousness of the issues involved, despite lobbying at the highest level and clear explanations of our need for a satisfactory response," British Foreign Secretary David Miliband told lawmakers at the House of Commons on Monday.

Russian businessman Andrei Lugovoi was named by British prosecutors as the chief murder suspect in the radiation poisoning death of former agent Alexander Litvinenko in London last year.
(AP Photo/ Misha Japaridze)

The government said the counter-measures, which include the suspension of visa facilitation negotiations with Russia, are meant to show the Kremlin Britain's displeasure with Russia's refusal to extradite Lugovoi so he can stand trial in London.

"The heinous crime of murder does require justice," Miliband said. "This response is proportional and it is clear at whom it is aimed.''

British prosecutors have named Lugovoi, a Russian businessman and former KGB spy, as the main suspect in the murder by radioactive poisoning of Alexander Litvinenko, also a former Russian spy.

Litvinenko defected from the KGB and then became a British citizen. He was known as a fierce critic of the Kremlin and Russian President Vladimir Putin. Investigators believe he was poisoned by a highly toxic dose of the radioactive isotope polonium 210, while meeting with Lugovoi at the Millennium Hotel in London on Nov 1, 2006. Litvinenko died in hospital roughly three weeks later.

Russian prosecutors said July 5 they would not co-operate with extraditing Lugovoi, who maintains his innocence, on the grounds that Russia's constitution does not allow Russian citizens to face criminal charges in foreign nations.

Britain also refuses to extradite Russians

Not since 1996, amid allegations of spying, has either country expelled one another's diplomats.

Miliband said the government has "chosen to expel four particular diplomats in order to send a clear and proportionate signal about the seriousness of the case," but would not identify the diplomats by name or specify their position. None of the Russian diplomats has left the country yet, he said.

The Kremlin has vowed to reciprocate if Britain follows through with its threat.

In a statement in Moscow, Russia's Foreign Ministry spokesman, Mikhail Kamynin, said "the provocative actions" of British authorities "will not go unanswered."

Russia also accused Britain of using the expulsions as part of a "well-staged" ploy to politicize the Litvinenko affair. The two countries are already embroiled in a diplomatic fight over Britain's refusal to extradite two anti-Kremlin Russians with asylum in Britain.

With files from the Associated Press