November 23 marks three years to the day that ex-KGB agent turned Kremlin critic Alexander Litvinenko died of polonium poisoning in a London hospital, aged 44.

The ensuing diplomatic spat over Russia’s refusal to extradite the chief suspect in the murder of Litvinenko, Russian businessman and now MP Andrei Lugovoy, caused a considerable chill in relations between Russia and the UK. Three years on, the case is no further forward: Russia still refuses to extradite Lugovoy, due to a constitutional ban on extraditing Russian citizens.

Litvinenko’s widow, Marina, who co-authored a book published in 2007 about her husband’s death entitled “Death of a Dissident: The Poisoning of Alexander Litvinenko and the return of the KGB”, chose to mark the third anniversary of her husband’s death by writing an editorial in the British daily the Times.

In this editorial, Marina Litvinenko renews accusations against what she calls the “two suspects” in the case: Lugovoy, but also Russian Prime Minister Vladimir Putin who was president at the time. On his deathbed, Alexander Litvinenko accused Putin of having ordered his killing.

Marina Litvinenko says that Putin “is the prisoner of his secrets” since “he cannot relinquish control without risking that his successor, for his own reasons, would decide to dig into the Litvinenko murder”.

She also accuses Russia, not for the first time, of “giving official backing to the two suspects” and calls this “cover-up” a “state crime”.

These comments come less than two weeks after prosecutors in Germany dropped charges, due to a lack of evidence, against Russian Dmitri Kovtun.

A business partner of Lugovoy, he was accused by Germany of involvement in the murder of Litvinenko and was suspected of leaving a trail of polonium behind him, notably in his ex-wife’s apartment in Hamburg. The closing of the case against Kovtun is seen as a setback for those in the UK hoping to eventually see Lugovoy extradited.

As for Lugovoy himself, he has renewed an offer to come to Britain to talk to Scotland Yard, but only on his terms. He said on Russia Today, “We would be ready to go there if firstly, the British resume the investigation; secondly, send all the materials they have here [to Moscow] to prove the basis of the charges and thirdly, we see their real initiative”.

However, it is likely that Lugovoy would also insist on not being arrested – an assurance the British government would never give.