The Russian state killed opposition leader Alexei Navalny using a poison developed from a dart frog toxin, the Foreign Office has said. Two years on from the death of Mr Navalny at a Siberian penal colony, Britain and its allies have pinned the blame on the Kremlin following analysis of material samples found on his body.

There is no innocent explanation for the toxin epibatidine being found on Mr Navalny's body, the Foreign Office said. Speaking from the Munich Security Conference, Foreign Secretary Yvette Cooper said: "Since Yulia Navalnaya announced the loss of her husband here in Munich two years ago, the UK has pursued the truth of Alexei Navalny's death with fierce determination. Only the Russian government had the means, motive and opportunity to deploy this lethal toxin against Alexei Navalny during his imprisonment in Russia. Today, beside his widow, the UK is shining a light on the Kremlin's barbaric plot to silence his voice."

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Western governments said laboratory testing had "conclusively confirmed" the presence of epibatidine, a toxin found in South American poison dart frogs and not naturally occurring in Russia.

They added that, given Navalny died in custody and the substance’s extreme toxicity, poisoning was "highly likely" to have caused his death.

Officials from the UK, France, Germany, Sweden and the Netherlands said their representatives had formally notified the Organisation for the Prohibition of Chemical Weapons of an alleged Russian breach of the Chemical Weapons Convention.

They also warned the findings raised concerns Moscow may not have destroyed all of its chemical weapons stockpiles and vowed to use "all policy levers" to hold Russia to account.

It also referenced the 2018 Salisbury poisoning in the UK, which led to the death of Dawn Sturgess.