Scientists from Porton Down have not been able to establish where the novichok nerve agent used to poison Sergei and Yulia Skripal was made.

Gary Aitkenhead, chief executive of the Defence Science and Technology Laboratory (DSTL) at Porton Down, told Sky News they were not yet able to prove it was made in Russia.

He said: "We were able to identify it as novichok, to identify that it was military-grade nerve agent.

"We have not identified the precise source, but we have provided the scientific info to Government who have then used a number of other sources to piece together the conclusions you have come to."

'We don't know source of nerve agent'

He said establishing its origin required "other inputs", some of them intelligence-based, that the Government has access to.


Mr Aitkenhead added: "It is our job to provide the scientific evidence of what this particular nerve agent is, we identified that it is from this particular family and that it is a military grade, but it is not our job to say where it was manufactured."

However, he confirmed the substance required "extremely sophisticated methods to create, probably something only in the capabilities of a state actor".

He said there was no known antidote to novichok.

Image: Mr Aitkenhead would not comment on whether Porton Down keeps novichok

Porton Down's boss 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.

The Foreign Office responded that they still believed Russia was behind the attack because of the wider "intelligence picture".

A spokesperson said: "We have been clear from the very beginning that our world leading experts at Porton Down identified the substance used in Salisbury as a novichok, a military grade nerve agent.

"This is only one part of the intelligence picture.

'Porton Down said it was Russia'

"As the Prime Minister has set out in a number of statements to the Commons since 12 March, this includes our knowledge that within the last decade, Russia has investigated ways of delivering nerve agents - probably for assassination - and as part of this programme has produced and stockpiled small quantities of novichoks.

"Russia's record of conducting state-sponsored assassinations; and our assessment that Russia views former intelligence officers as targets.

"It is our assessment that Russia was responsible for this brazen and reckless act and, as the international community agrees, there is no other plausible explanation."

The Defence Science and Technology Laboratory also responded to Mr Aitkenhead's comments, writing in a series of posts on Twitter: "Our experts have precisely identified the nerve agent as a novichok.

"It is not, and has never been, our responsibility to confirm the source of the agent.

"This chemical identity of the nerve agent is one of four factors used by the Government to attribute the use of chemical weapons in Salisbury to Russia.

"The Government's assessment has been clear from the start. Our chemical analysis is a key part of the Government's assessment, and this has not changed."

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.

Image: Porton Down's boss says there is 'no way' the nerve agent came from there

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".

Russian President Vladimir Putin has also called for a "thorough inquiry" into the incident.

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

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.

Image: Sergei Skripal and his daughter remain in hospital

Ms Skripal'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 Moscow's 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.

Moscow's deputy foreign minister, Alexander Grushko, said on Tuesday that the poisonings may have been set up by the UK to justify an increase in military spending.

In comments reported by Russian news agencies, Mr Grushko said the attempted murders could have been "arranged by Britain" because "they need a major enemy".

Image: Sergei Lavrov suggested the UK may have carried out the attack because of Brexit

His boss, foreign minister Sergei Lavrov, floated another possible motive on Monday: that the UK could have carried out the poisonings to distract from Brexit.

A retired Russian lieutenant general has also warned of a doomsday scenario and suggested the situation could escalate into the "last war in the history of mankind".

Evgeny Buzhinsky, who leads security think tank the PIR Center, told the BBC's Today programme he was "afraid that it will end up in a very, very bad outcome".

Asked to clarify, he said: "A real war, worse than a cold war is a real war, it will be the last war in the history of mankind."

Mr Buzhinsky said the West was "cornering Russia and to corner Russia is a very dangerous thing".

When asked if there was any realistic possibility of triggering war, a spokesman for Prime Minister Theresa May said: "We need to respond in a proportionate way to this aggressive behaviour from Russia and that's what we're doing."