Andrei Lugovoi, one of two men accused of poisoning the former spy, says findings are merely invention, presupposition and rumours

The former Russian spy Andrei Lugovoi has denounced the British inquiry that said he was one of the state-directed assassins of dissident Alexander Litvinenko, describing it as nonsense.

Speaking to the BBC, the former KGB bodyguard and FSB secret service agent dismissed the findings of Sir Robert Owen, chairman of the inquiry that said President Vladimir Putin likely approved the assassination of Litvinenko in London in 2006.

Lugovoi said: Ive assured the nonsense conclusions of your judge who has clearly gone mad. I insured nothing new there. I am very sorry that 10 years on nothing new has been presented, merely invention, presupposition, gossip.

And the fact that such terms as possibly and likely were used in the report, means there is no proof , nothing cement against us.

Lugovoi and a second man, Dmitry Kovtun, are believed to have killed Litvinenko by lacing a pot of tea given to him during a meeting at the Millennium hotel in central London with polonium-2 10, a lethal radioactive poison.

Both fled back to Russia and did not return to Britain to give evidence at the year-long investigation, which returned its findings on Thursday.

Lugovoi said the allegations were an open lie that were linked to exclusively political goals intended to escalate relations with the Kremlin.

Litvinenkos widow, Marina, called for all Russian intelligence agent to be thrown out of the UK and for further economic sanctions against Moscow. She said it would be unthinkable for the British government to ignore the findings of the Owen inquiry.

In a frank letter to David Cameron, Marina Litvinenko called for a firm reaction. She demanded travelling prohibitions and sanctions on at the least twelve someones. The listing included Putin, Nikolai Patrushev, the FSBs boss at the time, and other Russian state entities. She also intends to sue the Russian government in the British courts.

The home secretary, Theresa May, has signalled that the UK government had little craving for enforcing punitive measures on Russia, though she acknowledged that Litvinenkos murder amounted to a blatant and unacceptable breach of international law. The probable involvement of Putins Kremlin came as no surprise, May told the Commons.

May told MPs she would be asking Interpol to issue European arrest warrants for Lugovoi and Kovtun but proposed no wider action against the Russian state. This was an act of slaying that took place in the street of London and it was state-sponsored, she said. The conclusion that the Russian state was likely involved in the murder is deeply disturbing.

However, May added that there was a wider national security interest in retaining a guarded participation with Russia, including working with Russia is to ensure a peace settlement in Syria. She pointed out that it was impossible for Britain to seek to impose a travelling ban on a head of state, and said Britain had no illusions about the state of Russia.

The governments reaction also included a Treasury freeze of Lugovoi and Kovtuns assets. But Litvinenkos legal squad said the gesture was largely symbolic; her lawyer Ben Emmerson said it would be craven of the “ministers ” not to take farther action, after what Emmerson dubbed an act of nuclear state terror on the street of London.

Cameron, speaking from the world economic forum in Davos, said the murder was a shocking event but said it was necessary to continue to work with Russia. Do we at some level have to go on having some sort of relationship with them because we need a solution to the Syria crisis? Yes, we do but we do it with clear eyes and a very cold heart.

Dmitry Peskov, Putins press spokesman, dismissed the inquiry as a quasi-investigation. He ridiculed the judges use of likely and called his report an example of subtle British humour.

Putin has already ruled out any possibility of extradition in blunt terms. In 2007 the then foreign secretary, David Miliband, expelled four Russian diplomats in protest.

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