Image copyright Reuters

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> 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> 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.



Once again, Boris Johnson is a liability to Britain. Why is he still in the job? | Ellie Mae O’Hagan Read more

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> Media playback is unsupported on your device Media caption On the trail of Russians Alexander Petrov and Ruslan Boshirov, who UK police carried out a nerve agent attack in Salisbury in March 2018

Vladimir Putin must take responsibility for the Salisbury Novichok attack, UK security minister Ben Wallace has said.

Mr Wallace told the BBC "ultimately, of course", Russia's president was behind the poisoning of Russian ex-spy Sergei Skripal and his daughter in March.

The Kremlin, which denies involvement, said it was "unacceptable" to make accusations against the leadership.

The UK has named two men believed to be from Russia's military intelligence service, the GRU, as the main suspects.

Theresa May told the Commons on Wednesday that the suspects had entered the UK on Russian passports using the names Alexander Petrov and Ruslan Boshirov.

She said the poisoning was "not a rogue operation" and was "almost certainly" approved at a senior level of the Russian state.

Mr Skripal, 66, and his daughter Yulia, 33, were poisoned with Novichok on 4 March. Det Sgt Nick Bailey also fell ill after responding to the incident in Salisbury.

Prosecutors say there is sufficient evidence to charge the two men, and UK officials are due to brief the UN Security Council on the investigation on Thursday.

Police have also linked the attack to a separate Novichok poisoning on 30 June in Amesbury, that led to the death of 44-year-old mother-of-three Dawn Sturgess.

Meeting with the UN

Britain called Thursday's meeting of the UN Security Council, of which Russia is a permanent member, along with China and UK allies the US and France.

Mr Wallace said the UK must use the meeting to "maintain the pressure, to say the behaviour we have seen is totally unacceptable".

He said Mr Putin's government "controls, funds and directs the military intelligence - that's the GRU", adding that nobody could say the Russian leader was "not in control of his state".

BBC security correspondent Gordon Corera said that alongside the meeting, it was thought there would be less visible activity including covert work by British intelligence to disrupt the GRU.

Mrs May has also said Britain will push for the EU to agree new sanctions against Russia.

Ahead of the UN meeting, Australia said it was "in lock step with the UK on the importance of holding Russia to account" over the "dangerous and deliberate act".

What might the UK do to disrupt the GRU?

Analysis by BBC security correspondent Gordon Corera

The most effective measure, officials claim, may have already been taken in expelling suspected Russian intelligence officers in the UK and from allied countries.

Names will also be shared to prevent them being posted to each other's nations.

There will be the attempt to use publicity and exposure to make it harder for its officers to travel and operate.

Other measures against Russia more generally, it is hoped, might also push the Kremlin to restrain the GRU.

Finally, there will be a more clandestine element.

This is unlikely to mean "cyber-war", rather it will be attempts to disrupt the GRU's own cyber-operations to try to make its life harder.

Police appeal

Image copyright Metropolitan Police Image caption In the evening of 4 March, CCTV showed the pair at Heathrow Airport, where they were to board a flight to Moscow

Police are asking the public for information about a suitcase seen in the CCTV image of the two suspects at Heathrow Airport on Sunday 4 March, before they flew to Moscow.

In the image, Mr Petrov can be seen pushing a hard dark-coloured wheelie suitcase with a green stripe of the size that can fit into hand luggage lockers.

It does not appear that he arrived in the country with the suitcase.

Image copyright Metropolitan Police Image caption The pair are seen in the centre of Salisbury heading towards the train station

Counter terrorism officers are also interested in any information the public can give them about the grey and olive backpack that Mr Petrov and Mr Boshirov were both seen wearing at different times on the Sunday.

Moscow reaction: 'Go to hell'

By BBC Monitoring

Responding to the fresh accusations, the Kremlin's media machine resorted to its usual tactic: a combination of denials and sarcasm.

"Don't laugh," said a talk-show host on state TV, delivering the latest news from London.

The foreign ministry's spokeswoman, Maria Zakharova, put in an appearance herself to accuse the UK of fabricating the Skripal case. "This whole story was created to punish Russia... to introduce sanctions," she said on Rossiya 1 TV.

"A detective story" and "an absurd political thriller" were some of the epithets used by Russian news bulletins, which also claimed that Britain's allegations were not backed up by a shred of evidence.

At the same time, they dismissed the suspects' photographs released by London as crude fakery.

"Put evidence on the table or go to hell," said one commentator on Russian state TV.

The suspects' movements

Image copyright Metropolitan Police Image caption Police released CCTV showing the two men arriving at Gatwick Airport on 2 March

Image copyright Metropolitan Police Image caption They were seen arriving at Salisbury station the following day for what officers said was reconnaissance

The Metropolitan Police said the two men arrived at Gatwick Airport from Moscow on 2 March and stayed at the City Stay Hotel in Bow Road, east London.

On 4 March they travelled to Salisbury - having also visited for reconnaissance the previous day - where Mr Skripal's front door was contaminated with Novichok.

Image caption Yulia and Sergei Skripal fell ill after Mr Skripal's front door was sprayed with Novichok

Officers believe a modified perfume bottle was used to spray the door.

The pair flew from Heathrow to Moscow later that night.

Image copyright PA Image caption The hotel in east London, where police say Alexander Petrov and Ruslan Boshirov stayed before they travelled to Salisbury, is "open for business as usual"

While traces of Novichok were found in the London hotel room, police said there was no risk to other guests who were staying at the hotel at the time.

Officers want to hear from anyone who was a guest there from 4 March to 4 May.

The Crown Prosecution Service (CPS) said Petrov and Boshirov should be charged with offences including conspiracy to murder; attempted murder and the use and possession of Novichok contrary to the Chemical Weapons Act.

However, it is not applying to Russia for the extradition of the two men, because Russia does not extradite its nationals.

But a European Arrest Warrant has been obtained in case the pair travel to the EU.

Amesbury poisoning

Image copyright Facebook Image caption Dawn Sturgess and Charlie Rowley were poisoned by Novichok

Police said Ms Sturgess and her partner Charlie Rowley were later exposed to Novichok in Amesbury, near Salisbury, after handling a contaminated container, labelled as Nina Ricci Premier Jour perfume.

Mr Rowley told police he found the box containing the small bottle and an applicator - all found to be counterfeit - in a charity bin.

He tried to put the two parts together and got some of the contents on himself. His partner Ms Sturgess applied some of the contents to her wrists and became unwell.

The bottle, with a modified nozzle, had contained a "significant amount" of Novichok, Scotland Yard said.

Image copyright AFP/Met Police Image caption The counterfeit perfume bottle recovered from Mr Rowley's home and the box police say it came in.

The charges Petrov and Boshirov would face currently relate only to the Salisbury attack. Police said officers are continuing to work with the Crown Prosecution Service on the Amesbury incident. </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". </s> Media playback is unsupported on your device Media caption 'Absolute evidence' needed in Salisbury poisoning case

Jeremy Corbyn wants to see "incontrovertible evidence" before blaming Russia for the poisoning of an ex-spy and his daughter in Salisbury.

The Labour leader said it was "clear" the nerve agent used was "very similar" to those made in Russia - and Moscow should be challenged about this - but "absolute" proof was still needed.

He also said the international chemical weapons watchdog needed greater powers.

Boris Johnson said to deny Russian involvement was "quite extraordinary".

Russian ex-spy Sergei Skripal and his daughter Yulia were found slumped on a park bench in Salisbury on 4 March.

The government says they were exposed to a military-grade nerve agent belonging to the Novichok group, and accuses Russia of being behind the poisoning. Russia denies any involvement.

On Sunday, the Bishop of Salisbury called for a deeper and lasting solution to the diplomatic fallout between the UK and Russia, during a service of cleansing in the city centre.

'Appalled and alarmed'

The Organisation for the Prohibition of Chemical Weapons (OPCW) has said it agrees with the UK's findings on the identity of the nerve agent.

The UK's national security adviser has since said that Russian intelligence agencies targeted Ms Skripal's emails as early as 2013, and that Moscow trained "special units" to use nerve agents.

In a letter to Nato, Sir Mark Sedwill also accused Russia of testing assassination methods with chemical weapons, including using nerve agents smeared on to door handles.

When asked on the Andrew Marr Show what it would take for Mr Corbyn to agree that the Russian state had committed the attack, he said: "I want to see incontrovertible evidence of it.

"I am appalled and alarmed at the idea that anyone would use this nerve agent and clearly it was an attempt to murder the Skripals on British soil.

"Sadly it's not the [OPCW's] job to identify who made it or necessarily where it was made. I think we do need to strengthen the role of the OPCW in the future."

When asked whether he agreed with Shadow Chancellor John McDonnell that the poisoning was a state-sponsored assassination attempt, Mr Corbyn said: "If we're going to make a very clear assertion like that we've got to have the absolute evidence to do it."

Media playback is unsupported on your device Media caption Denial of Russian involvement in Salisbury poisoning is "perplexing", says Boris Johnson

Mr Johnson, also speaking to Andrew Marr, said: "To continue to deny the likelihood of Russian involvement, of a state-sponsored assassination attempt, I think is quite extraordinary."

He added that it was a "blindness to reality that I find very perplexing, a defiant refusal to accept the Kremlin was responsible for this".

Image caption Sergei Skripal remains in hospital but his daughter Yulia has been discharged

The Skripals are thought by police to have come into contact with the nerve agent on the front door handle of their home in Wiltshire.

The Skripals and Det Sgt Nick Bailey - who was exposed to the Novichok when he was tending to the Skripals - were all treated at Salisbury District Hospital.

The police officer and Ms Skripal, 33, have been discharged. Mr Skripal is "still seriously ill" but his condition is said to be improving.

Areas of the city were cordoned off as special investigators collected samples to test for the nerve agent.

Blessing the city

On Sunday, the Bishop of Salisbury hosted a "service of cleansing and celebration" to symbolically reclaim the city for the common good.

The Right Rev Nicholas Holtam said: "It's a service in which we want to thank the community that have really carried Salisbury through this.

"For some it's had an impact in a whole variety of ways, it's had an impact on business, it's had an impact on people's mental health."

Following the service, clergy blessed the city, near the spot where the Skripals were found.
UK Leader of the Opposition Jeremy Corbyn of Labour asks to see "incontrovertible evidence" before accepting Russia was responsible. Foreign Secretary Boris Johnson responds, saying it is "quite extraordinary" to question Russian involvement.