The alleged murder of ex-Russian spy Alexander Litvinenko in 2006 was ‘probably’ approved by Vladimir Putin, according to a new report – and it may have been because he suggested the Russian leader had sex with young boys.

Sir Robert Owen, a retired High Court judge, yesterday released his findings on the death of the Russian dissident who was poisoned with Polonium-210 in the Pine Bar of London’s Millennium Hotel, Mayfair.

Sir Robert wrote in his report: “There was undoubtedly a personal dimension to the antagonism between Mr Litvinenko on the one hand and President Putin on the other.

“Mr. Litvinenko made repeated highly personal attacks on President Putin culminating in the allegation of paedophillia in July 2006.”

Litvinenko published an article on the Chechenpress website four months before his death, shortly after Putin was filmed bizarrely lifting up the shirt of young boy outside the Kremlin and kissing him on the stomach.

He claimed that “before his graduation, his bosses learned that Putin was a pedophile [sic].”

He went on to say that after becoming director of the Russian security service, the FSB, “Putin found videotapes in the FSB Internal Security directorate, which showed him making sex with some underage boys.”

Sir Robert described this article as “of the most serious nature”, and concluded that “members of the Putin administration, including the president himself and the FSB, had motives for taking action against Litvinenko, including killing him, in late 2006.”

Putin – who first became Russian president in 2000 – has repeatedly made homophobic comments in the past, often linking homosexuality to paedophilia. Before the Sochi Winter Olympics he told reporters that Russia does not ban gay relationships, just “the propaganda of homosexuality and paedophilia,” adding “we are not forbidding anything and nobody is being grabbed off the street, and there is no punishment for such kinds of relations. You can feel relaxed and calm, but leave children alone please.”

In 2013, Putin signed the gay propaganda law which made it illegal to distribute materials promoting “non-traditional sexual relationships” to minors, but recently condemned homophobia and pledged his support for LGBT rights.