By Michael Holden
LONDON (Reuters) - The lawyer for the family of former KGB agent Alexander Litvinenko, who was murdered in London in 2006, accused Britain and Russia on Tuesday of colluding to try to shut down an inquiry into his death for the sake of lucrative trade deals.
Litvinenko, who had been granted British citizenship and had become a vocal critic of Russian leader Vladimir Putin, died after someone slipped polonium-210, a rare radioactive isotope, into his cup of tea at a plush London hotel.
At a pre-inquest hearing at London's Royal Courts of Justice, lawyers for Litvinenko's widow said Britain was now trying to keep secret details of his work for its MI6 intelligence service, and material which showed Russia was behind his death.
"It is crucial, absolutely crucial, that the outcome of this hearing is to scotch, once and for all, any possible suggestion that it is because (British Prime Minister) David Cameron is interested in promoting trade with Russia that he is trying to close down the truth about this inquest," said Marina Litvinenko's lawyer, Ben Emmerson.
British police and prosecutors say there is enough evidence to charge two former KGB agents, Andrei Lugovoy and Dmitry Kovtun, with murder, while Litvinenko put his name to a deathbed statement accusing Putin of ordering his death to silence him, a claim dismissed by the Kremlin as nonsense.
Russia refused to extradite Lugovoy, who denies any involvement in the killing, and ties between Britain and Russia fell to a post-Cold War low in the immediate aftermath.
However, Cameron has sought to improve relations and strengthen business links since he came to power in 2010.
He secured 215 million pounds ($325 million) worth of business deals during a flying 24-hour visit to Russia in September, 2011. Britain has been the fifth-largest investor in the Russian economy since the 1991 fall of the Soviet Union, according to Russian statistics.
At Tuesday's hearing, lawyers for British Foreign Secretary William Hague argued sensitive information held by the government about Litvinenko should be subject to a public interest immunity (PII) certificate, preventing it from being publicly revealed.
"SERIOUS HARM TO PUBLIC INTEREST"
"The disclosure of material would pose a real risk of serious harm to public interest," said lawyer Neil Sheldon. Hague, he said, had considered all other options but had concluded nothing short of a PII certificate would be sufficient.
At a hearing in December, a lawyer acting on behalf of the inquest indicated Britain held information which established "a prima facie case as to the culpability of the Russian state".
Emmerson said withholding such material would defeat the whole purpose of the inquest, which is held under British law when a person dies unexpectedly to determine the cause of death.
"He (Hague) is approaching his coverup responsibilities, and that is what they are, with alacrity and enthusiasm," said Emmerson. "We can't allow Her Majesty's Government, by misusing the PII system, to force this inquest to dance to the Russian tarantella."
He mocked the government's "neither confirm nor deny" policy on whether Litvinenko, 43, was a paid MI6 agent, saying his legal team had evidence he was.
He said if the coroner, High Court judge Robert Owen, granted the PII request, he could potentially be shown secret evidence which conclusively showed the Kremlin was complicit in murder, but would then have to issue a public judgment which exonerated Russia of any involvement.
"This has all the hallmarks of a situation which is shaping up to become a stain on British justice," said Emmerson.
Owen, who earlier said the long-delayed full inquest was now unlikely to start on May 1 as planned, said he would give his ruling on the PII certificates on Wednesday morning.
Hague said on his Twitter page on Tuesday that he would be meeting Russia's Foreign and Defence Ministers London on March 13 to discuss foreign policy and "bilateral issues".
($1 = 0.6618 British pounds)
(Editing by Louise Ireland)