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Labour has called for an investigation into whether Boris Johnson "misled" the public over Russian involvement in the Salisbury nerve agent attack.

Labour leader Jeremy Corbyn earlier implied the foreign secretary had exaggerated the findings of the UK's defence laboratory, Porton Down.

Mr Johnson responded that Mr Corbyn's remarks were "lamentable".

Meanwhile, the international chemical weapons body has rejected Russian calls for a joint inquiry into the case.

Former Russian double-agent Sergei Skripal and his daughter Yulia remain in hospital after being poisoned by a nerve agent on 4 March.

The incident has caused a major diplomatic fallout, with the expulsion of some 150 Russian diplomats by the UK and its allies being met by counter-expulsions by Moscow.

Labour said in an interview given to German TV last month, Mr Johnson said that "people from Porton Down" were "absolutely categorical", adding: "I asked the guy myself. I said 'are you sure?', and he said 'there's no doubt'."

But on Tuesday the Porton Down laboratory said it could not verify the precise source of the Novichok nerve agent used, although it did say it was likely to have been deployed by a "state actor".

Labour called on the prime minister to launch an investigation into whether Mr Johnson broke the ministerial code.

'Egg on his face'

Shadow Cabinet Office minister, Jon Trickett, said Mr Johnson had "serious questions to answer".

"He clearly previously indicated that Porton Down had told him 'categorically' that Russia was the source of the nerve agent," he said.

Mr Corbyn said the foreign secretary had "egg on his face for the statement he made on German television".

"Either the foreign secretary has information that he's not sharing with Porton Down or it was a bit of exaggeration," he added.

Mr Johnson hit back on Twitter.

"It is lamentable that Jeremy Corbyn is now playing Russia's game and trying to discredit the UK over Salisbury attack," he wrote, setting out what he said were the "key facts".

He added: "28 other countries have been so convinced by UK case they have expelled Russians. In contrast, Jeremy Corbyn chooses to side with the Russian spin machine."

The UK has said that identifying the substance at Porton Down was "only one part of the intelligence picture".

It comes as Russia has also sought to discredit the UK's accusations.

Russia pointed to a now-deleted tweet by the Foreign Office which suggested Porton Down had "made clear" the nerve agent was "produced in Russia".

It had sought a joint inquiry after the UK blamed it for being the source of the Novichok nerve agent used.

Russia accused the UK of blocking access to an investigation being carried out by the Organization for the Prohibition of Chemical Weapons.

But it lost by 15 votes to six, while 17 member states abstained.

Following the verdict, Mr Johnson said Russia had failed in its attempts to "obscure the truth" and "derail the proper international process".

Image copyright EPA/ Yulia Skripal/Facebook Image caption Sergei Skripal, 66, and his daughter Yulia, 33, were poisoned by a nerve agent called Novichok

Russia has said the comments from Porton Down's chief executive Gary Aitkenhead reveal the UK's case to be "nothing but assumptions".

The Foreign Office said the deleted tweet had been part of a real-time account of a speech by the UK's ambassador in Moscow and was deleted because it "did not accurately report our ambassador's words".

It added: "None of this changes the fact that 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.

"No other country has a combination of the capability, the intent, and the motive to carry out such an act."

BBC diplomatic correspondent James Landale said Mr Johnson's "loose language" plus the deleted tweet represented a "self-inflicted wound" by the UK.

This had "muddied the waters" and allowed Russia to cast doubt on the UK's assessment, he said - but he added that the "international alliance" supporting the UK's position was "still holding". </s> The Labour party is calling on Boris Johnson to answer some “very serious questions” after it emerged that scientists have not been able to identify the origin of the Novichok nerve agent.

The foreign secretary previously claimed in an interview to German TV station, Deutsche Welle, that he had been told in “categorical” terms by Porton Down scientists that there was “no doubt” Russia was the source of the nerve agent used in the Salisbury poisoning of the Skripals.

READ MORE: Did Boris Johnson lie that lab told him Russia was source of Salisbury nerve agent? (WATCH VIDEO)

Opposition leader Jeremy Corbyn says Johnson now needs to answer some questions. “Where does that leave the Foreign Secretary? Egg on his face for the statement he made on German television.”

“Boris Johnson seems to have completely exceeded the information that he had been given and told the world in categorical terms what he believed had happened and its not backed up by the evidence he claimed to have got from Porton Down in the first place. Boris Johnson needs to answer some questions,” Corbyn told Sky News.

Corbyn also criticized the Foreign Office for issuing a tweet reiterating Johnson’s statement following the interview and then deleting it, Tuesday, following the announcement from Porton Down. Shadow home secretary, Diane Abbott also highlighted the decision by the Foreign Office to delete the tweet.

Meanwhile the Foreign Office is standing by its assessment that Russia is responsible for the attack. In a tweet Tuesday it said “it is not and has never been our responsibility to confirm the source of the agent.”

Abbott accused the Foreign Office of misleading the public about the Porton Down novichok evidence in a statement. “It seems Boris Johnson misled the public when he claimed that Porton Down officials confirmed to him that Russia was the source of the nerve agent used in the Salisbury attack.

Those officials have made it clear they cannot identify its source, and are not able to definitively say it came from Russia or elsewhere.”

Abbot added that Johnson’s actions once again show he is unable to responsibly represent Britain on the world stage.

Shadow education secretary, Angela Rayner also called on Johnson to answer “some very serious questions,” adding “the usual bluff bluster” will not do.

Corbyn was attacked by the Tories and some of his own MPs for his apparent ‘weak’ response to alleged Russian aggression. Several Labour MPs condemned Corbyn’s position and accepted Theresa May’s assessment of Russian culpability.

The Labour leader took a more cautious approach to the Skripal poisoning calling for the utilisation of proper channels of international law before attributing blame. </s> Boris Johnson has accused Jeremy Corbyn of "playing Russia's game" for challenging him over an interview on the Salisbury poisoning.

The Foreign Secretary said it was "lamentable" he was called upon to answer "serious questions" for appearing to suggest scientists at Porton Down were in "no doubt" the nerve agent came from Russia. </s> Boris Johnson under pressure to explain whether position has changed after tweet blaming Moscow is deleted

This article is more than 1 year old

This article is more than 1 year old

Boris Johnson is facing embarrassing questions over his claims that Russia had produced the Salisbury nerve agent after it emerged that the Foreign Office had deleted a tweet blaming Moscow for the attack.



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With the foreign secretary already under pressure over his remarks two weeks ago that a Porton Down scientist had been “absolutely categorical” that the novichok had originated in the country, Jeremy Corbyn accused Johnson of “completely exceeding the information he had been given” after the emergence of the deleted tweet.

Play Video 0:32 Jeremy Corbyn questions Boris Johnson's claim on Russian-made novichok – video

But Johnson later hit back, accusing the Labour leader of “playing Russia’s game”.

The deletion, immediately seized on by the Russian embassy, has deepened the government’s difficulties after British scientists at the UK’s defence research laboratory announced on Tuesday that they had not established that the nerve agent used to poison Sergei and Yulia Skripal had been made in Russia.

After Porton Down said it had “not identified the precise source” of the poison, the Foreign Office issued a swift rebuttal saying the prime minister had always been clear that the assessment was “only one part” of the intelligence picture.

Play Video 0:26 'Absolutely categorical': Boris Johnson insists novichok was made in Russia – video

The announcement prompted claims from the Kremlin that Britain was lying about the origins of the novichok and demanded an apology from Theresa May.

However, it emerged on Wednesday that the Foreign Office had earlier deleted a tweet claiming the British scientists had concluded that the nerve agent was “produced in Russia”.

In an awkward development for the Foreign Office, the Russian embassy’s Twitter feed pointed out that the 20 March tweet on a presentation by Britain’s ambassador to Moscow on the Salisbury attack had disappeared.

Russian Embassy, UK (@RussianEmbassy) Why would @foreignoffice delete this tweet from 22 March? pic.twitter.com/Nvu1BfJw9J

The deleted tweet read: “Analysis by world-leading experts at the Defence Science and Technology laboratory at Porton Down made clear that this was a military grade nerve agent produced in Russia.”

Johnson is now under growing pressure to explain whether the government has shifted its position.

Timeline Boris Johnson's diplomatic gaffes as foreign secretary Show Hide Johnson has caused a string of diplomatic incidents with his words and actions Footage emerges of Johnson reciting inappropriate poem in Myanmar Visiting the Shwedagon Pagoda, the most sacred Buddhist site in Myanmar's former capital Yangon, Johnson starts reciting Rudyard Kipling's colonial-era poem The Road to Mandalay. UK ambassador Andrew Patrick steps in and stops him. The poem includes a reference to the Buddha as a “Bloomin’ idol made o’ mud/ Wot they called the Great Gawd Budd” Johnson refers to clearing away 'dead bodies' in Sirte At a Conservative conference fringe event Johnson draws gasps saying: “There’s a group of UK business people who want to invest in Sirte, on the coast, near where Gaddafi was captured and executed. They literally have a brilliant vision to turn Sirte into the next Dubai. The only thing they’ve got to do is clear the dead bodies away." Tory colleague Heidi Allen says the remarks are "100% unacceptable from anyone, let alone the foreign secretary”. A senior Downing Street source says: “We did not feel it was an appropriate choice of words.” Johnson disputes Nazanin Zaghari-Ratcliffe's reason for visiting Iran "When I look at what Zaghari-Ratcliffe was doing, she was simply teaching people journalism, as I understand it" the foreign secretary tells the foreign affairs committee. He is later forced to apologise in parliament, accepting that the British government believes, as Zaghari-Ratcliffe and her family assert, that the sole purpose of her visit to Iran was for a holiday. Despite a subsequent visit to Tehran by Johnson, Zaghari-Ratcliffe remains in prison, serving a five-year sentence. Compares Irish border Brexit question to London congestion charge While applying pressure over Brexit arrangements, a leaked document reveals Johnson had suggested the government’s task is not to maintain “no border” in Ireland, but to prevent it from “becoming significantly harder”. On the radio he goes on to say "There’s no border between Islington, Camden and Westminster, but when I was mayor of London we anaesthetically and invisibly took hundreds of millions of pounds from people travelling between those boroughs without any need for border checks.” Claims Porton Down informed him novichok source was Russia In an interview with Deutsche Welle's Zhanna Nemtsova, Johnson categorically asserts Porton Down informed him the nerve agent came from Russia. Nemtsova: You argue the source of this nerve agent, novichok, is Russia. How did you manage to find it out so quickly? Does Britain possess samples? Johnson: Let me be clear with you … When I look at the evidence, I mean the people from Porton Down, the laboratory … Nemtsova: So they have samples …? Johnson: They do. And they were absolutely categorical and I asked the guy myself, I said, "Are you sure?" and he said there's no doubt.



The security minister, Ben Wallace, said the Porton Down scientists had only provided one part of the picture and had never been expected to attribute responsibility for the attack.

He told the BBC: “Scientists are scientists. I, as well as national security, have organised crime [and] terrorism under my portfolio, and when we work with forensic scientists, the scientists tell us what something is. They tell me a gun and a type of gun was used, but the attribution of who used it, exactly how it was used, is a matter for the broader investigation.



“That includes intelligence, detectives if it’s a police investigation, and the scientists as well, and that’s perfectly understandable.”

Wallace, a close ally of the foreign secretary, defended Johnson for suggesting he had received assurances from government scientists that the nerve agent was categorically made in Russia.

“Porton Down will be able to tell you there are very, very, very few people in the world who, first of all, did design novichok – and that was the Russians – and who have developed and stockpiled it. In fact, the task of that is reduced to one,” he said.

A Foreign Office spokesman said: “An HMA Moscow [British ambassador Laurie Bristow] briefing on 22 March was tweeted in real time by @UKinRussia and amplified by @foreignoffice to explain what happened in Salisbury to as wide an audience as possible.



“One of the tweets was truncated and did not accurately report our ambassador’s words. We have removed this tweet.”

According to an official transcript of the speech, Bristow’s original words were: “The analysts at Porton Down, the Defence Science and Technology Laboratory in the UK, established and made clear that this was a military-grade chemical weapon. One of the novichok series; a nerve agent as I said produced in Russia.”

Corbyn, who faced criticism for his initial, cautious response to the novichok allegations, accused Johnson of exaggerating the evidence that Russia was to blame for the Salisbury poisoning.

Quick guide What is novichok? Show Hide Novichok refers to a group of nerve agents developed by the Soviet Union in the 1970s and 80s to elude international restrictions on chemical weapons. Like other nerve agents, they are organophosphate compounds, but the chemicals used to make them, and their final structures, are considered classified in the UK, the US and other countries. The most potent of the novichok substances are considered to be more lethal than VX, the most deadly of the familiar nerve agents, which include sarin, tabun and soman. While the novichok agents work in a similar way, by massively over-stimulating muscles and glands, one chemical weapons expert said the agents did not degrade fast in the environment and had 'an additional toxicity that was not well understood. Treatment for novichok exposure would be the same as for other nerve agents, namely with atropine, diazepam and potentially drugs called oximes. The chemical structures of novichok agents were made public in 2008 by Vil Mirzayanov, a former Russian scientist living in the US, but the structures have never been publicly confirmed. It is thought they can be made in different forms, including as a dust aerosol. The novichoks are known as binary agents because they only become lethal after mixing two otherwise harmless components. According to Mirzayanov, they are 10 to 100 times more toxic than conventional nerve agents. While laboratories that are used to police chemical weapons incidents have databases of nerve agents, few outside Russia are believed to have full details of the novichok compounds and the chemicals needed to make them. Photograph: Matt Cardy/Getty Images Europe

The Labour leader, asked on a campaign visit to Watford about the foreign secretary’s remarks, said: “He claimed categorically – and I think he used the words 101% – that it had come from Russia.

“Boris Johnson seems to have completely exceeded the information that he had been given and told the world in categorical terms what he believed had happened. And it’s not backed up by the evidence he claimed to have got from Porton Down in the first place. Boris Johnson needs to answer some questions.

He added that Johnson had been left with “egg on his face” over his interview.

In a series of tweets on Wednesday afternoon, Johnson dismissed Corbyn’s response, writing: “It is lamentable that Jeremy Corbyn is now playing Russia’s game and trying to discredit the UK over Salisbury attack... 28 other countries have been so convinced by UK case they have expelled Russians. In contrast, Jeremy Corbyn chooses to side with the Russian spin machine.”

The European commission said it had never thought that Porton Down had been tasked with identifying the source of the substance used in Salisbury.

The commission spokesman Alexander Winterstein told a Brussels press briefing: “Our understanding is that the role of the experts there was to identify the type of agent that was used, not the source of the agent ... They did identify the nerve agent novichok. That is what they have done.” </s> Mr Johnson made the comments after the chief executive of the Porton Down military facility admitted there was no proof linking the Novichok nerve agent used in the March 4 attack on Sergei and Yulia Skripal to Russia. Asked why the UK believed that Russia was the source of the nerve agent, Mr Johnson said: "The people from Porton Down, the laboratory, they were absolutely categorical. I asked them that myself. I said 'Are you sure?'. He said 'There's no doubt'."

Commenting on Mr Johnson's interview, a Government spokesman said: "The Foreign Secretary was making clear that Porton Down were sure it was a Novichok - a point they have reinforced. "He goes on in the same interview to make clear why based on that information, additional intelligence and the lack of alternative explanation from the Russians, we have reached the conclusion we have. "What the Foreign Secretary said then, and what Porton Down have said recently, is fully consistent with what we have said throughout. It is Russia that is putting forward multiple versions of events and obfuscating the truth." The Foreign Office also deleted a tweet insisting the novichok used in the Salisbury attack was definitely "produced in Russia". The tweet on March 22, said: "Analysis by world-leading experts at the Defence Science and Technology Laboratory at Porton Down made clear that this was a military-grade novichok nerve agent produced in Russia."

Labour leader Jeremy Corbyn has accused Mr Johnson of "exaggeration" over the evidence that Russia was to blame for the Salisbury poisoning. Speaking during a local election campaign visit to Watford, Mr Corbyn said: "He claimed categorically - and I think he used the words 101% - that it had come from Russia. Porton Down have not said that, they said that they've identified it as Novichok, they cannot identify the source of it. "Either the Foreign Secretary has information that he's not sharing with Porton Down or it was a bit of exaggeration. I don't know which it is, but I think we need a responsible, cool approach to this.

"We need to get to the source of this to prevent it ever happening again." Shadow home secretary Diane Abbott challenged the Foreign Secretary to explain his earlier comments. She said: ”It seems Boris Johnson misled the public when he claimed that Porton Down officials confirmed to him that Russia was the source of the nerve agent used in the Salisbury attack.

"Those officials have made it clear they cannot identify its source, and are not able to definitively say it came from Russia or elsewhere. "Boris Johnson is supposed to represent Britain on the world stage, but time and again he has shown he is unable to do so responsibly." Explaining the deletion of the tweet, a Foreign Office spokesman said it had been an inaccurate summary of comments made by the UK's ambassador to Russia, Laurie Bristow, at a briefing in Moscow. Referring to Dr Bristow as "HMA" - Her Majesty's Ambassador - the spokesman said: "A full transcript and video of the briefing have been available on GOV.UK since 22 March. "An HMA Moscow briefing on 22 March was tweeted in real time by @UKinRussia and amplified by @foreignoffice, to explain what happened in Salisbury to as wide an audience as possible. One of the tweets was truncated and did not accurately report our ambassador's words. We have removed this tweet." </s> Boris Johnson is facing embarrassment over his claims about the Salisbury poisoning attack after the Foreign Office deleted a tweet claiming Russia had produced the nerve agent. The Foreign Secretary was under pressure to explain the change as the Russian Embassy in London ridiculed Britain’s stance linking Moscow to the attempted murder of former double agent Sergei Skripal and his daughter Yulia. Jeremy Corbyn said that Johnson had been “left with egg on his face” and had some “serious questions to answer”. Ministers were already on the defensive after the head of the Porton Down defence laboratory revealed on Tuesday that it had “not identified the precise source” of the poison. But in a further blow, it emerged that the FCO had deleted a tweet claiming that the UK’s leading defence scientists had indeed concluded that the nerve agent was “produced in Russia”. HuffPost has found a cached version of the deleted tweet.

Contrary to the FCO tweet, the ambassador had not stated that Porton Down had itself “made clear” that the Salisbury poison had been “produced in Russia”. A Foreign Office spokesman confirmed that the message had indeed been deleted, stating that it had not been an accurate reflection of the account given by Bristow. “An HMA [Her Majesty’s Ambassador] Moscow briefing on 22 March was tweeted in real time by @UKinRussia and amplied by @foreignoffice, to explain what happened in Salisbury to as wide an audience as possible,” the spokesman said. “One of the tweets was truncated and did not accurately report our Ambassador’s words. We have removed this tweet.” Foreign Office sources confirmed that the tweet had been removed on Wednesday. The FCO also put out a full transcript of the ambassador’s remarks in his briefing on the Salisbury attack.

The row had been sparked on Tuesday after Gary Aitkenhead, the chief executive of the Defence Science and Technology Laboratory at the facility, told Sky News on Tuesday that the lab had not identified the nerve agent as made in Russia. Shadow Home Secretary Diane Abbott suggested that Aitkenhead also cast doubt on Boris Johnson’s claim that Vladimir Putin was ‘unequivocally’ to blame for the attempted murder of a former Russian spy and his daughter. “It seems Boris Johnson misled the public when he claimed that Porton Down officials confirmed to him that Russia was the source of the nerve agent used in the Salisbury attack,” she said in a statement. “Those officials have made it clear they cannot identify its source, and are not able to definitively say it came from Russia or elsewhere. “Boris Johnson is supposed to represent Britain on the world stage, but time and again he has shown he is unable to do so responsibly.” Critics seized on the contrast between the scientists’ caution and the Foreign Secretary’s interview with a German news channel in which he declared British defence experts had told him that the Kremlin was behind the attack on Sergei and Yulia Skripal. Asked directly how he could assert that the source of the Novichok nerve agent was Russia, the Foreign Secretary replied that he had ‘interrogated’ the scientists. He then told DW.com: “People from Porton Down, they were absolutely categorical. I asked the guy myself I said ‘are you sure?’ and he said there’s no doubt.”

A Foreign Office spokesman told HuffPost suggested he was only referring to the fact that the agent was a ‘Novichok’ not that it was made in Russia. “The Foreign Secretary was making clear that Porton Down were sure it was a Novichok – a point they have reinforced. “He goes on in the same interview to make clear why based on that information, additional intelligence and the lack of alternative explanation from the Russians, we have reached the conclusion we have. “What the Foreign Secretary said then, and what Porton Down have said recently, is fully consistent with what we have said throughout. It is Russia that is putting forward multiple versions of events and obfuscating the truth.” Jeremy Corbyn faced criticism from Tories and some of his own MPs last month when he asked for more evidence to show Putin had ordered the attack, and refused to rule out the possibility that Moscow had lost control of the material. Abbott told BBC Radio 4’s Today programme that Corbyn had been vindicated for his stance, while Johnson’s own approach begged new questions. “I can’t speak in detail about the briefing. It doesn’t surprise me that Porton Down are saying this because the security services were always very cautious in what they said,” she said. “What surprised me was that so many people were willing to rush onto the media and say it was unequivocally Putin. That’s not necessarily what we were told.” “Boris Johnson going on international media and saying he was 101% certain it was Putin. I don’t understand where he got that information from. “We will I hope get some credit for taking a more thoughtful approach and asking the right questions.” Although Aitkenhead stressed that the nerve agent’s production was “something only in the capabilities of a state actor [ie a Government]”, Downing Street was forced to point out on Tuesday that Porton Down provided “only one part of the intelligence picture” that pointed to Moscow’s responsibility. The defence lab was forced to tweet a clarification too.

But Russia pounced on Aitkenhead’s remarks. Vladimir Putin’s spokesman, Dmitry Peskov, said Britain would have to apologise to Russia for its “mad accusations”. The Russian embassy in London said the UK’s claims that Moscow was behind the attack was a “bluff”. Hamish de Bretton-Gordon, a chemical weapons expert and former commander of the British Army’s Joint Chemical, Biological, Radiological and Nuclear Regiment, urged the Government to counter Russian ‘disinformation’ by producing its own evidence as to why Moscow was to blame. “Security organisations are always very circumspect about giving the evidence because it can betray a source,” he told the Today programme. “What is clear now is that somebody in the government, whether it is the Foreign Secretary or the Prime Minister, needs to lay out exactly what the supporting evidence is, that is compelling, that doesn’t betray sources. </s> It is beyond reasonable doubt that Russia was behind the Salisbury attack, Security Minister Ben Wallace insisted as Moscow stepped up efforts to undermine the UK’s case.

Russia has called for a meeting of the United Nations Security Council and foreign minister Sergey Lavrov said the UK has “legitimate questions” to answer about the nerve agent assault on Sergei Skripal and his daughter Yulia.

But Mr Wallace said that the investigation’s “roads lead to Russia” as the UK sought to maintain diplomatic pressure on Moscow over the incident.

Russia called a meeting of the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague on Wednesday to insist its experts must be involved in the testing programme and probe.

But it lost the vote after Britain told the extraordinary meeting the demand was a sign the federation was “nervous” of what the inquiries will find.

Russian officials speaking after the meeting concluded said they had presented a “common sense” case and pointed to the “lies by Tony Blair” over Iraq as they criticised the intelligence about the attack.

But Mr Wallace told BBC Radio 4’s Today programme that comparisons to the flawed intelligence on weapons of mass destruction in Iraq were not valid.

“There’s no missing nerve agent that no-one can find – it was used in Salisbury, we had three people seriously ill, two obviously remain in hospital in critical condition, and there is no doubt that we have found nerve agent,” he said.

[quote]That nerve agent has been identified to being manufactured we believe in Russia and we believe that the nerve agent, the Novichok type of nerve agent, is only capable of being produced by a nation state, and then we add that to intelligence we hold, we add that to some of the police investigation that’s going on right now, and we can say that roads lead to Russia, that we are beyond reasonable doubt of the view that the Russian state is behind this.[/quote]

Labour leader Jeremy Corbyn has also raised the subject of the “flawed intelligence and dodgy dossiers” behind the Iraq invasion in his response to the Skripal case.

Mr Wallace said the Labour leader had seen more intelligence “than the average backbench MP” because he had received a Privy Council briefing on the matter – but added: “The circle of who gets to see very sensitive information is very small because if you leak it or it gets out, people’s lives are put at risk.”

Foreign Secretary Boris Johnson – who has come under fire over his handling of the incident – has accused Mr Corbyn of siding with the “Russian spin machine”.

Moscow has asked for an open session of the UN Security Council to be held on Thursday at 8pm UK time.

Tension between Moscow and London has risen after the head of the Porton Down military research facility said scientists had not verified Russia as the source of the substance used in the attack on the Skripals.

Vladimir Putin seized on the comments from the chief executive of the Government’s Defence Science and Technology Laboratory (DSTL), Gary Aitkenhead, as he accused the UK of launching an “anti-Russian campaign”.

But UK security services have a high degree of confidence that they have pinpointed the location of the Russian laboratory that manufactured the nerve agent used in the attack, according to The Times.

A Whitehall source told the newspaper: “We knew pretty much by the time of the first Cobra (the emergency co-ordination briefing that took place the same week) that it was overwhelmingly likely to come from Russia.”

The Foreign Secretary, who has faced claims he exaggerated the evidence against Moscow, said countries around the world “continue to share our assessment” about the nerve agent attack.

He said: “The international community has yet again seen through these tactics and robustly defeated Russia’s attempts today to derail the proper international process.”

In the latest sign of the international storm created by the Salisbury attack, expelled US diplomats appeared to be leaving Moscow.

Russia last week ordered 60 American diplomats to leave the country by Thursday in retaliation for the United States expelling the same number of Russians. </s> The Foreign Office has deleted a post on its Twitter feed stating that British scientists had established the Novichok nerve agent used in the Salisbury poisoning came from Russia.

Foreign Secretary Boris Johnson has come under fire after an announcement on Tuesday that Porton Down scientists had not verified the source of the chemical believed to have been used in the March 4 attack on Sergei and Yulia Skripal.

The tweet, issued on 22 March, said: “Analysis by world-leading experts at the Defence Science and Technology Laboratory at Porton Down made clear that this was a military-grade Novichok nerve agent produced in Russia.”

Explaining the deletion of the tweet, a Foreign Office spokesman said it had been an inaccurate summary of comments made by the UK’s ambassador to Russia, Laurie Bristow, at a briefing in Moscow.

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Referring to Dr Bristow as “HMA” - Her Majesty’s Ambassador - the spokesman said: “A full transcript and video of the briefing have been available on GOV.UK since 22 March.

“An HMA Moscow briefing on 22 March was tweeted in real time by @UKinRussia and amplified by @foreignoffice, to explain what happened in Salisbury to as wide an audience as possible. One of the tweets was truncated and did not accurately report our ambassador’s words. We have removed this tweet.”

READ MORE: Salisbury poisoning: Porton Down can’t verify nerve agent is Russian

In an interview on German TV on 20 March when he was asked why the UK believed that Russia was the source of the nerve agent, Mr Johnson said: “The people from Porton Down, the laboratory, they were absolutely categorical. I asked them that myself. I said ‘Are you sure?’. He said ‘There’s no doubt’.”

Labour leader Jeremy Corbyn said Mr Johnson either had information that he had not shared with the laboratory or it was a “bit of exaggeration” and called for a “responsible” approach to the situation.

Mr Corbyn said: “He claimed categorically - and I think he used the words 101% - that it had come from Russia. Porton Down have not said that, they said that they’ve identified it as Novichok, they cannot identify the source of it.

“Either the Foreign Secretary has information that he’s not sharing with Porton Down or it was a bit of exaggeration. I don’t know which it is, but I think we need a responsible, cool approach to this.”

Russia’s proposal for a new, joint investigation into the poisoning was voted down at the international chemical weapons watchdog at The Hague last night. Russia has accused Britain of blocking access to an investigation being carried out by the Organisation for the Prohibition of Chemical Weapons. Britain earlier said Russia’s call for an inquiry with the UK was “perverse”.

Russia lost the vote by 15 votes to six, while 17 member states abstained. China, Azerbaijan, Sudan, Algeria and Iran were among the countries that backed Russia’s motion. </s> Boris Johnson is facing questions over a conversation he recounted with Porton Down officials about the Salisbury attack.

The Foreign Secretary was urged to explain the answer he gave when asked why he was certain the novichok nerve agent originated in Russia.

On Tuesday, Britain's military research unit revealed to Sky News it was not yet able to establish where the substance used to poison Sergei and Yulia Skripal was made.

Gary Aitkenhead, chief executive of the Defence Science and Technology Laboratory (DSTL) at Porton Down, said scientists had not "identified the precise source".

"But," he added, "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".

It came two weeks after Mr Johnson gave an interview to the German broadcaster Deutsche Welle, and was asked why he believed the chemical came from Russia.

He said: "When I look at the evidence, I mean the people from Porton Down, the laboratory..."

Mr Johnson was asked if they had samples.

He said: "They do. And they were absolutely categorical and I asked the guy myself, I said, 'Are you sure?' And he said, 'There's no doubt'."

After Mr Aitkenhead's comments to Sky News, the Foreign Office released a statement saying it had been "clear from the very beginning" that Porton Down had identified the type of substance as novichok.

"This is only one part of the intelligence picture," a spokesperson said.

They cited Prime Minister Theresa May's announcement that Russia has for the last decade "investigated ways of delivering nerve agents probably for assassination".

The spokesperson added: "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."

When asked for clarification on Mr Johnson's comments about Russia being the source, a Foreign Office source told Sky News he "misspoke", but that they could "see that" interpretation.

Responding, Labour MP Chris Williamson wrote on Twitter: "Dear Britain, Boris Johnson is your Foreign Secretary and he just lied to justify our country's foreign policy. How does that make you feel?"

And shadow home secretary Diane Abbott shared another post that said: "Listen, in his own words, to Boris Johnson claim he had categorical assurances from Porton Down that the nerve agent originated from Russia. This has today been exposed as incorrect."

Previously, Mrs May had cited Porton Down research to back up the Government's stance against Russia.

She said that "positive identification of this chemical agent by world-leading experts at the Defence Science and Technology Laboratory" was one of the pieces of evidence.

She also highlighted "knowledge that Russia has previously produced this agent and would still be capable of doing so, Russia's record of conducting state-sponsored assassinations and our assessment that Russia views some defectors as legitimate targets for assassinations".
Jeremy Corbyn, leader of the opposition Labour Party, calls for an investigation into comments by UK Foreign Secretary Boris Johnson. Johnson is facing criticisms he overstated the strength of evidence against Russia, an accusation he calls "lamentable" and accuses Corbyn of sympathizing with Russia.