Russian President Vladimir Putin is a "tin pot despot" who, with Kremlin "cronies," was behind the 2006 poisoning murder of ex-KGB agent Alexander Litvinenko in London, the lawyer for his widow said on Friday.
Kremlin critic Litvinenko died three weeks after drinking green tea laced with radioactive polonium-210 at London's plush Millennium hotel.
British authorities say there is evidence to try Russians Andrei Lugovoy and Dmitry Kovtun with murder, while from his deathbed, Litvinenko accused Putin of ordering his killing.
Both Russians deny any involvement and the Russian government has rejected any link to the death, questioning the British motives for making such accusations after Litvinenko's killing plunged Anglo-Russian relations to a post-Cold War low.
On the closing day of a British public inquiry into the death, Ben Emmerson, the lawyer for Litvinenko's widow Marina, said scientific evidence which linked Kovtun and Lugovoy to traces of polonium across London proved beyond doubt that they were responsible for the murder.
He said tests of the sink in the bathroom of Kovtun's room at the Millennium Hotel revealed quantities of polonium which could only be achieved by direct contact with the rare isotope.
"The same scientific evidence ultimately proves beyond doubt that the murder was commissioned by the Russian state," Emmerson said.
The lawyer said that on the very day back in March when the inquiry was hearing evidence that he argued clearly showed Kovtun's involvement, Putin was awarding a medal of honour for services to the Motherland to Lugovoy.
It was a "menacing gesture of support," Emmerson said, designed to intimidate the inquiry.
"It was a crass and clumsy gesture from an increasingly isolated tin pot despot, a morally deranged authoritarian who was at that very moment clinging desperately onto political power in the face of international sanctions and a rising chorus of international condemnation," he said. "After years of negotiation and appeasement, the world has lost its patience now with Mr Putin's judo politics and his cringing hard-man photo opportunities."
Emmerson said Kovtun, Lugovoy and the Russian state had attempted to manipulate and undermine the independent inquiry, most recently when Kovtun pulled out of giving evidence by videolink this week.
He added: "That approach speaks volumes and proves significant support for the conclusion that Mr. Putin and his cronies were not only behind the murder but now stand four-square behind the murderers."