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.”

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.

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.

“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.

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.

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”.

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.”

The UK has directly accused Russia’s military intelligence agency, the GRU, of being behind a number of cyber attacks that took place between 2015 and 2017, calling them “indiscriminate and reckless” with a range of target types including political institutions, businesses, media and even sport.
It says the chaotic campaign of attacks by the GRU shows it is “working in secret to undermine international law and international institutions”.
The government has also identified 12 hacker group it believes the GRU to be associated with — including ‘Fancy Bear’, a group behind a string of cyber espionage attacks including the 2016 hack of the Democratic National Committee, which the government is also now directly linking to Russia’s military spy agency.
Of course it’s not the first time the Kremlin has been linked to politically motivated attacks (some of which haven’t even required actual hacking).
Nor is it the first time the GRU has been specifically linked to Fancy Bear. Cybersecurity firm Crowdstrike made the same link back in 2016 — with “high level confidence“.
But it’s a first for the UK government to make a link and public accusation of Russia for the attacks — likely intended to keep up geopolitical pressure on president Putin in the wake of the Sailsbury poisonings which it has also previously linked to two GRU agents. (The Kremlin later claimed the two were just tourists who happened to have been visiting the town on the same day as a former Russian double agent and his daughter were poisoned with a nerve agent.)
The UK’s National Cyber Security Center, which is a public-facing branch of the UK’s GCHQ spy agency, has published the latest cyber attack claims — writing that it has “identified that a number of cyber actors widely known to have been conducting cyber attacks around the world are, in fact, the GRU”.
“These attacks have been conducted in flagrant violation of international law, have affected citizens in a large number of countries, including Russia, and have cost national economies millions of pounds,” it adds.
The full list of hacker groups being linked to the Kremlin and “almost certainly” to the GRU — with what the NCSC calls “high confidence” — are:

• APT 28
• Fancy Bear
• Sofacy
• Pawnstorm
• Sednit
• CyberCaliphate
• Cyber Berkut
• Voodoo Bear
• BlackEnergy Actors
• STRONTIUM
• Tsar Team
• Sandworm

The other cyber attacks the government has now also publicly attributed to the GRU include:

• an October 2017 ransomware attack by BadRabbit, which encrypted hard drives and rendered IT inoperable — resulting in disruption including to the Kyiv metro, Odessa airport, Russia’s central bank and two Russian media outlets
• an August 2017 attack on the World Anti-Doping Agency in which confidential medical files relating to a number of international athletes were released
• a phishing-based attack on an unnamed small UK-based TV station, which took place between July and August 2015, in which multiple email accounts were accessed and content stolen

The government also lists two attacks it says it had previously attributed to the GRU:

• a June 2017 cyber attack that targeted the Ukrainian financial, energy and government sectors but which also spread to impact other European and Russian businesses
• an October 2017 attack involving the VPNFILTER malware which infected thousands of home and small business routers and network devices worldwide. The NCSC notes that the infection “potentially allowed attackers to control infected devices, render them inoperable and intercept or block network traffic”

Commenting in a statement, foreign secretary Jeremy Hunt said:

These cyber attacks serve no legitimate national security interest, instead impacting the ability of people around the world to go about their daily lives free from interference, and even their ability to enjoy sport.
The GRU’s actions are reckless and indiscriminate: they try to undermine and interfere in elections in other countries; they are even prepared to damage Russian companies and Russian citizens.  This pattern of behaviour demonstrates their desire to operate without regard to international law or established norms and to do so with a feeling of impunity and without consequences.
Our message is clear: together with our allies, we will expose and respond to the GRU’s attempts to undermine international stability.

At the time of writing the Russian Embassy’s UK Twitter account had not yet issued any trolling responses to the UK government.
Well, unless this is it…

KIEV (Reuters) – Ukraine’s interior minister said on Tuesday a suspect in the Skripal poisoning case, working for Russian military intelligence, had been identified in Ukraine as a man who helped the former Ukrainian president flee to Russia in 2014.

It was not immediately clear whether minister Arsen Avakov was citing information from Ukrainian intelligence or quoting the accounts of journalists. He released a statement following a meeting with a British minister.
His spokesman declined to comment further. A lawyer for former President Viktor Yanukovich, who escaped to Russia in February 2014 during a wave of street protests, has previously denied that the Skripal suspect had helped Yanukovich.
Former Russian double agent Sergei Skripal and his daughter Yulia were found slumped on a public bench in the English city of Salisbury in March. Britain says they were poisoned with a nerve agent administered by Russian intelligence officers.
The Skripals survived, but a woman who lived in the area, unconnected with them, later died from what British police say was contact with the poison used, which her partner had found in a discarded perfume bottle.
Russia denies any involvement in the affair, which has deepened its international isolation.
Moscow says two Russian men suspected by British authorities, captured on surveillance footage near the scene of the poisoning, were innocent tourists visiting Salisbury twice during a weekend trip to Britain. London says that explanation is so far-fetched as to all but prove Russia’s involvement.
“Interior Minister Arsen Avakov noted that one of the participants in the attack in the Salisbury, an officer of the GRU of the Russian Federation, had been recognised in Ukraine as a person who had been involved in transporting ex-president Yanukovich from Ukraine,” the minister’s statement said.
Avakov did not identify which of the two Skripal suspects had helped Yanukovich escape.

Skripal referred disparagingly to Ukrainians as “simply sheep who needed a good shepherd.”

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