By Estelle Shirbon
LONDON (Reuters) - The London High Court has quashed the British government's decision not to hold a public inquiry into the murder of former Russian spy Alexander Litvinenko, who died in London in 2006 after being poisoned with a radioactive substance.
Tuesday's judgment means the government will have to reconsider the decision, a diplomatically sensitive one as a public inquiry could delve into the issue of whether Russia was involved in the killing. Moscow denies any hand in it.
Litvinenko, 43, died after drinking tea poisoned with a rare radioactive isotope, polonium-210, in a plush hotel. From his deathbed he accused Russian President Vladimir Putin of ordering his murder, a charge the Kremlin has rejected.
The High Court stopped short of calling for a public inquiry, but said that Home Secretary Theresa May, the interior minister who refused to order such an investigation, would have to revisit the issue.
"If she is to maintain her refusal, she will need better reasons than those given in the decision letter," wrote Lord Justice Richards, handing down the unanimous judgment of three High Court justices.
The Home Office, or interior ministry, said it was carefully considering the judgment.
Litvinenko's widow Marina, who had brought the challenge against May's decision to the High Court, welcomed the ruling.
"I have never been able to see why the British government should want to protect the people in the Kremlin who ordered my husband's murder," she said in a statement.
"This was the murder of a British citizen on the streets of London using radioactive poison. You would have thought that the government would want to get to the bottom of who was behind it."
Robert Owen, the coroner in charge of the inquest into Litvinenko's death, had requested a public inquiry. May turned down his request in July.
An inquest, a British legal process that takes place in cases of violent or unnatural deaths, is separate from any public inquiry. Owen had said his examination of any Russian complicity would be flawed because he could not consider secret evidence held by the British government.
"The case for setting up an immediate statutory inquiry as requested by the coroner is plainly a strong one," the High Court said.
In a formal submission to the court, Owen had written that the secret evidence "does establish a prima facie case as to the culpability of the Russian state in the death of Alexander Litvinenko".
Lawyers for the former KGB agent's family have argued that Britain wanted to stifle any investigation for fear of jeopardizing business deals and souring ties with Moscow which were badly damaged by the poisoning.
Relations deteriorated to a post-Cold War low after British police and prosecutors said there was enough evidence to charge two former KGB agents, Andrei Lugovoy and Dmitry Kovtun.
Home Secretary May had said she had taken into account the interests of Britain's relations with Russia in deciding not to order a public inquiry, but this had not been the main factor.
In Tuesday's judgment, the High Court said there were "strong reasons of public interest" why the issue of Russian state responsibility should be investigated.
(Additional reporting by Michael Holden, editing by Stephen Addison and Alistair Lyon)