Updated 19:55

Russian leader Vladimir Putin has called for an inquiry into the Salisbury attack after the United Kingdom’s chemical weapons research facility admitted it is unable to say where the nerve agent used in the attack came from.

This afternoon Gary Aitkenhead chief executive of the UK Defence Science and Technology Laboratory (DSTL) at Porton Down in Wiltshire said scientists were only able to confirm the substance involved was novichok – a military-grade nerve agent developed by Russia from the 1970s onward.

He said scientists cannot prove the agent used in Salisbury was made in Russia.

Britain has insisted the Russian state was behind the attack - with Russian diplomats expelled from Ireland, the UK, US, Canada, Australia and countries across Europe in response.

British Prime Minister Theresa May has claimed there is “no alternative conclusion other than that the Russian state was culpable” for the attack.

That position has been backed by the Irish government and the EU.

Russian President Vladimir Putin delivers a speech in Ankara Turkey, 04-04-2018. Image:  Mustafa Kaya/Xinhua News Agency/PA Images

Speaking during a state visit to Turkey, Russian President Valdimir Putin said novichok could havbe been manufactured in as many as 20 different nations.

Given the lack of precise information about the nerve agent's origin, he also lamented "the speed at which the anti-Russian campaign has been launched," adding that it "causes bewilderment."

"The president of a laboratory within eight kilometres of the location where the incident took place told the news agencies they could not tell whether this was manufactured in Russia," he said.

Source

In an interview with Sky News this afternoon Mr Aitkenhead said: "We were able to identify it as Novichok; to identify that it was military-grade nerve agent.”

“We have not verified the precise source but we 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,” he said.

He said that his researchers were able to identify what the agent is, what “particular family” it came from and that it is military grade but insisted “it is not our job to say where it was manufactured."

Questions

It comes as the Russian Ambassador to Ireland suggested the British Government could have been behind the attack.

Yuri Filatov claimed that the British authorities have questions to answer, alleging: "If they choose to ignore them, there is ample ground to assume that we're dealing with a grand-scale provocation organised by London with the aim to discredit Russia."

His comments come after the Russian Foreign Minister Sergei Lavrov warned that the poisoning could have been in Britain’s interests.

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Sophisticated

Mr Aitkenhead said novichok requires "extremely sophisticated methods to create, something only in the capabilities of a state actor."

He said there was no known antidote to novichok, and that none was administered to either of the Skripals.

He would not comment on whether the lab had developed or keeps stocks of novichok, but dismissed suggestions the substance used to poison the Skripals had come from Porton Down.

"There is no way anything like that could have come from us or left the four walls of our facility," said Mr Aitkenhead.

It comes as the chemical weapons watchdog said it would hold a special meeting on Wednesday into the UK government's claim that Russia was behind the attack.

General view of a sign for Porton Down Science Campus near Salisbury in England, 15-03-2018. Image: Andrew Matthews/PA Wire/PA Images

Denial

Russia has vehemently denied accusations from Britain that it was behind the poisoning.

Russia's embassy in the UK said it "understood from the very start" that Whitehall statements on the nerve agent having been produced in Russia were "a bluff."

"Now this has been confirmed by the head of the secret lab," it added.

"This only proves that all political declarations on the Russian origin of the crime are nothing but assumptions not stemming from objective facts or the course of the investigation."

The embassy also claimed that novichok may be present in the UK.

"We have also noted that, like in his earlier interview, Mr Aitkenhead is not denying that the lab had developed or keeps stocks of the agent they call 'novichok', although, of course, he would not admit it," it added.

Chemical weapons watchdog

The OPCW (Organisation for the Prohibition of Chemical Weapons) said its executive council would meet in the morning in The Hague.

In a letter, Russia's ambassador to the OPCW, Alexander Shulgin, asked for the meeting to discuss Britain's allegations "in a confidential sitting."

OPCW experts have taken samples from Salisbury to try to verify the nerve agent used and its origin.

Nerve agent

Former spy Sergei Skripal and his daughter Yulia were poisoned four weeks ago in Salisbury.

Russia has been pushing hard for access to the pair, saying it "insists" on seeing them.

Yulia's condition improved significantly last week and she is now said to be conscious and talking. Her father, however, remains unresponsive and critical.

The UK government has said it is looking into the legality of the request and also considering "the rights and wishes" of the 33-year-old.

The diplomatic row has led to more than 100 diplomats being expelled from the UK, Russia, the US and Europe, and the war of words shows no signs of dying down.

With reporting from Paul Quinn and IRN ...