Russia has called an extraordinary meeting of the world’s chemical weapons watchdog to protest the UK government’s allegation it was behind the poisoning of a former Russian spy and his daughter in Salisbury.
Britain blamed Russia for the attack on Sergei Skripal and his daughter Yulia with a military-grade nerve agent, plunging diplomatic relations between the East and West to their lowest levels since the Cold War.
Moscow fiercely denies any involvement and has demanded to take part in the British investigation.
The meeting of the Organisation for the Prohibition of Chemical Weapons (OPCW) was called by Russia to “address the situation around allegations of non-compliance” with the chemical weapons convention made by the UK against Moscow.
It came a day after the head of the Porton Down military research facility said his scientists could not trace the nerve agent’s precise source.
Gary Aitkenhead, the chief executive of the Government’s Defence Science and Technology Laboratory (DSTL), said the poison used in Salisbury had been identified as a military-grade novichok nerve agent which could probably be deployed only by a nation-state.
But he told Sky News it was not Porton Down’s role to work out where the agent came from and suggested the government’s conclusion it was highly likely to have come from Russia was based on “a number of other sources”.
Asked about his scientists’ findings, Mr Aitkenhead told Sky: “We in terms of our role were able to identify it as novichok, to identify it was a military-grade nerve agent.
“We have not verified the precise source, but we have provided the scientific information to the government, who have then used a number of other sources to piece together the conclusions that they have come to.
“It’s our job to provide the scientific evidence that identifies what the particular nerve agent is. We identified that it was from this family and that it’s a military-grade nerve agent. It’s not our job to say where that actually was manufactured.”
The location of manufacture “can be established through a number of different input sources which the Government has access to,” he said, adding: “From our perspective, scientific evidence is only one of those sources, and it requires a number of other things to verify that.
“It’s a military grade nerve agent which requires extremely sophisticated methods in order to create – something that’s probably only within the capabilities of a state actor.”
Porton Down’s identification of the substance as novichok was a key point in the evidence presented by the UK in Theresa May’s successful bid to recruit international support in the dispute with Moscow, resulting in the expulsion of more than 100 Russian diplomats from over 20 countries.
Citing Mr Aitkenhead, Russia’s president, Vladimir Putin, called for a thorough investigation into the poisoning during a visit to Turkey, where he said “the speed at which the anti-Russian campaign has been launched causes bewilderment.”
The DSTL stressed on Twitter its evidence was only part of the intelligence picture and said: “It is not, and has never been, our responsibility to confirm the source of the agent.”
A spokesman for the Foreign Office said: “Russia has called this meeting to undermine the work of the OPCW, which, fully in accordance with the chemical weapons convention, is providing the UK with technical assistance and evaluation through independent analysis of samples from the Salisbury attack.
“Of course, there is no requirement in the chemical weapons convention for the victim of a chemical weapons attack to engage in a joint investigation with the likely perpetrator.
“This Russian initiative is yet again another diversionary tactic, intended to undermine the work of the OPCW in reaching a conclusion.”
A Downing Street spokesman said: “As the Prime Minister has made clear, the UK would much rather have in Russia a constructive partner ready to play by the rules.
“But this attack in Salisbury was part of a pattern of increasingly aggressive Russian behaviour, as well as a new and dangerous phase in Russian activity within the continent and beyond.”
The meeting of the OPCW executive council on Wednesday will be held behind closed doors at The Hague.