Theresa May's National Security Council met today to discuss a suspected attempt to assassinate a former Russian spy.

The council, thought to include the heads of the intelligence services and senior ministers alongside other officials, was updated on the investigation, which is now being led by counter terrorism police.

Downing Street refused to confirm further details on who was invited and exactly what was discussed or decided.

The meeting came after Foreign Secretary Boris Johnson told MPs Britain would not hesitate to impose new punishment on Russia if it was found to be responsible for the suspected attack on Sergei Skripal, 66, in Salisbury on Sunday.

He suggested Britain could partially boycott the World Cup in Russia this summer by refusing to send officials or diplomats alongside players.

Mr Johnson said: 'If things turn out to be as many members suspect that they are... I think we will have to have a serious conversation about our engagement with Russia.

'And for my part I think it will be difficult to see how, thinking ahead to the World Cup this summer, I think it would be difficult to imagine that UK representation at that event could go ahead in the normal way.

'We will certainly have to consider that.'

Sources close to Mr Johnson later insisted he was referring to officials and dignitaries attending the tournament and not footballers.

The World Cup begins in Russia in June. England are the only UK team to have qualified to take part.

Boris Johnson (pictured in the Commons today) has vowed 'robust' action if it is proven Russia was behind a suspected poisoning attack on a former spy

The Foreign Secretary (pictured today responding to an urgent question) told MPs the Government would stand up for the 'lives, values and freedoms' of British people

Sergei Skripal is fighting for his life after being exposed to an unknown substance. He is a former colonel of Russia's military intelligence, was convicted in Russia in 2006 on charges of espionage for Britain's MI6 intelligence agency

Mr Johnson hinted at a range of new sanctions as he insisted any attempt to kill on British soil 'will not go unsanctioned or unpunished'.

The Foreign Secretary told MPs the Government would stand up for the 'lives, values and freedoms' of people in Britain.

He branded Russia a 'malign and disruptive' force in the global community and said Britain would continue to stand up against it, even if the nation is force to 'pay a price' for doing so.

Mr Johnson was summoned to the Commons after Tom Tugendhat, the chairman of the Foreign Affairs Committee, secured an emergency debate on Russia's 'soft war' against the West.

WHAT SANCTIONS COULD BE IMPOSED ON RUSSIA? Foreign Secretary Boris Johnson today hinted at a new range of sanctions if it is proven Russia is behind a suspected assassination attempt in London. The intervention came after Tory MP Tom Tugendhat revived calls for a 'Magnitsky List' to be set up in Britain. It would mirror US laws imposing travel bans on senior Kremlin officials responsible for the death of Russian accountant Sergei Magnitsky in a prison in 2009. UK ministers have repeatedly refused to pass a similar law, but has imposed financial sanctions on several senior Russian figures. Further sanctions could see UK assets owned by Kremlin officials seized and travel bans on more individuals imposed. The intent is to stop the ruling elite in Moscow travelling freely and keeping money abroad while Putin operates with little restraint. Advertisement

The warning comes after shadow defence secretary Diane Abbott warned ministers not to allow 'London and the Home Counties to become a kind of killing field for the Russian state'.

British relations with Russia have been chilly since President Vladimir Putin was suspected of personally ordering the attack on Litvinenko.

Defence Secretary Gavin Williamson yesterday repeated warnings of the military threat from Russia, warning Putin had 'hostile intent' toward Britain.

Downing Street today said all relevant departments, including No 10, were being updated on the police investigation.

Mr Johnson told the Commons: 'Police, together with partner agencies, are now investigating. MPs will note the echoes of the death of Alexander Litvinenko in 2006.

'And while it'd be wrong to prejudge the investigation, I can reassure the House that should evidence emerge that implies state responsibility, then Her Majesty's Government will respond appropriately and robustly.'

'It is too early to speculate as to the precise nature of the crime or attempted crime that has taken place in Salisbury.

'But I know members will have their suspicions.

Mr Johnson (pictured at the Despatch Box today) hinted at a range of new sanctions as he insisted any attempt to kill on British soil 'will not go unsanctioned or unpunished

'And what I will say to the House is that if those suspicions prove to be well-founded then this Government will take whatever measures we deem necessary to protect the lives of the people in this country, our values and our freedoms.

'Though I am not now pointing fingers, I say to governments around the world that no attempt to take innocent life on UK soil will go either unsanctioned or unpunished.'

Mr Johnson said it may be that the UK will 'continue to pay a price' for standing up to Russia, adding he hopes MPs from all parties will support the Government's approach.

He said: 'I'm afraid that the events in Salisbury may very well - and again we must be very careful in what we say because it is too early to prejudge the investigation - but if the suspicions that I know on both sides of the House prove to be well-founded then it may very well be that we are forced to look again at our regime, our sanctions regime and other measures that we may seek to put in place.'

It was suggested last night that Vladimir Putin (pictured today) would never have forgiven Mr Skripal following his treason conviction

Russian president Vladimir Putin (pictured today) once hinted at how his country deals with spies by insisting that 'traitors always end in a bad way'

Foreign Affairs Committee chairman Tom Tugendhat (file) said if proven the possible poisoning of Sergei Skripal, 66, would a new escalation in a 'soft war' against the UK'rob

Diane Abbott (file image) today demanded answers from ministers about an apparent attack on a Russian spy she said had 'striking similarities' to the murder of Alexander Litvinenko

The Russian Embassy posted a short response to Mr Johnson's address to MPs, saying ironically: 'We are impressed by the statement of the Foreign Secretary in Parliament today. The Foreign Secretary spoke in such a manner as if the investigation was already over and Russia was found responsible for what had happened in Salisbury.'

The statement continued: 'We regret that instead of a proper official clarification on the issue the Foreign Secretary chose to threaten Russia with retribution. Looks like the script of yet another anti-Russian campaign has been already written.'

Skripal who had recently told police he feared for his life, was rushed to hospital after collapsing on a bench outside a shopping centre in Salisbury on Sunday.

'Poisoned spy case' echoes fate of Alexander Litvinenko - Putin critic killed by polonium-laced tea Relations between Britain and Russia have been strained since the murder of ex-KGB agent Alexander Litvinenko in London in 2006, a killing which a judge said was probably approved by President Vladimir Putin. The defector died after two agents slipped radioactive polonium 210 into his tea pot at a Mayfair hotel in central London, according to an inquiry headed by former high court judge Sir Robert Owen. The inquiry found two Russian men - Andrei Lugovoi and Dmitri Kovtun - had deliberately poisoned Litvinenko by putting polonium-210 into his drink at a London hotel, leading to an agonising death. Alexander Litvinenko died after two agents slipped radioactive polonium 210 into his tea It said the use of the radioactive substance - which could only have come from a nuclear reactor - was a 'strong indicator' of state involvement and that the two men had probably been acting under the direction of the FSB. Possible motives included Litvinenko's work for British intelligence agencies, his criticism of the FSB, and his association with other Russian dissidents, while it said there was also a 'personal dimension' to the antagonism between him and Putin. International arrest warrants issued for Mr Lugovoi and Mr Kovtun remain in force although Russia continues to refuse their extradition. The Millennium Hotel in Mayfair, where he is said to have been poisoned In a statement to mark the 10th anniversary of his death, Marina Litvinenko said her husband - who she called Sasha - had been an 'extraordinary man' whose courage in speaking out against the Russian security service, the FSB, had left an enduring legacy. While she acknowledged Mr Putin had refused to accept the inquiry's findings, she said it remained open for other world leaders to take action against the Russian state and that she hoped her struggle to find the truth had not been in vain. 'It has taken 10 long years for the truth to be established and for Sasha's dying words that President Putin was responsible for his death to be proved to be true,' she said. 'I know that Mr Putin's Russia does not accept the findings of the British public inquiry and will continue to deny the truth in the face of overwhelming evidence. 'But those findings are now part of history and the rest of the world understands the difference between truth and propaganda. And that is what matters to me. 'What action world leaders will take against the ever vengeful Russian state in these dramatic times remains to be seen. I hope and pray that my struggle has not been in vain.' Last year the scandal took a new twist when Scotland Yard detectives who investigated the Litvinenko case revealed they too had been poisoned by the Russians in an extraordinary attempt to thwart the inquiry. The inquiry found Andrei Lugovoi (left, in 2007) and Dmitri Kovtun (right, in 2006) - had deliberately poisoned Litvinenko Detective Inspector Brian Tarpey, who flew to Moscow to investigate, says: ‘I remember one evening my officer [a colleague who travelled with him] was complaining of stomach cramp and not being very well. ‘Next morning I accompanied him to the general prosecutor’s office. We were offered tea. I had no hesitation in accepting. ‘After we left, I started to feel a little bit uncomfortable. Not wanting to put too fine a point on it, I had the s***s. ‘I have no doubt in my mind that someone poisoned us with something like gastroenteritis.’ Advertisement

He was found with a 33-year-old woman, who is also fighting for her life. She is thought to be a family member.

Health chiefs said the pair had been exposed to an 'unknown substance'.

Mr Tugendhat said that if Russian involvement was proved, the Skripal case would amount to a further salvo in a 'soft war against the UK' conducted by Mr Putin's administration.

'It is too early to say whether it is certain or not, but it certainly bears all the hallmarks of a Russian attack,' Mr Tugendhat said.

'If it is, then I am calling for a whole-of-Government response.

'Too much of this has been left to the Foreign Office or the Home Office separately.

'What needs to be done is for the whole Government to get involved in responding to what amounts to a soft war against the UK, taking in the cyber-hacking they have done and the various aggressions they have been involved in.'

Mr Tugendhat said that the eventual response to any Russian involvement in the Skripal case could include travel bans, sanctions and the imposition of Magnitsky Sanctions legislation allowing the assets of human rights violators to be frozen in the UK.

Theresa May's official spokesman referred questions about the incident to the police while officers 'establish the facts'.

The spokesman said: 'All relevant departments, including No 10, are being kept informed of developments as you'd expect.

'This is an ongoing investigation that's being led by the police and it's an operational matter for them.'

The Government's emergency 'Cobra' committee has not been convened to discuss the incident.

Ms Abbott told the BBC Radio 4 Today programme: 'It's important not to speculate without knowing everything it but it does bear a striking similarity to the death of Litvinenko who was poisoned by the Russian state and before that Markov who was killed bizarrely by somebody stabbing him with an umbrella with poison on the tip.

'That was put to the Russian state and the problem with these things is sometimes truth is stranger than fiction.'

Ms Abbott highlighted a BuzzFeed investigation that named as many as 14 people who died in suspicious circumstances linked to Russia.

She said the cases did not need to be reopened but that the Home Secretary should reassure the public all of them were probed properly after they were exposed over the past two years.

Ms Abbott added: 'I will be writing to Amber Rudd to say if it does prove to be the case the Russian state is involved in thus latest death what assurances can she give about the rigour of the investigation and where we go from here.

'I don't like defaulting to a red menace analysis but we can't allow London and the Home Counties to become a kind of killing field for the Russian state.'

Ms Abbott's intervention came as the Government remained tight lipped about the circumstances surrounding Skripal.

Julian Lewis, the chairman of the Commons defence committee, told MailOnline: 'If a second Russian former spy has been targeted in the UK, after the reckless use of polonium to kill Mr Litvinenko, it shows that the Kremlin has not the slightest interest in a positive relationship with the West and has learned nothing from the outrage caused by its previous public act of murder.'

Labour MP Chris Bryant, who chairs the All-Party Parliamentary Group on Russia, called for a Government minister to come to the despatch box today to update the Commons on what is known about the Skripal case.

Mr Bryant said: 'We have got to be a little careful about establishing the facts - and I very much hope a Government minister will come to the chamber later today to explain what we do know - but we know Putin's record of using excessive violence.

'There is a long list of Putin opponents who have been bumped off around the world. The fact that this happens just before presidential elections, I would suspect, is not circumstantial.

'We can't be having Russian operatives bumping people off in the UK. I was very critical of both David Cameron and Theresa May in the 2010 Parliament because they kept refusing to allow a full investigation of the Litvinenko murder. It was years before Theresa May finally allowed one to happen.

'If something similar has occurred in this situation, then we shouldn't let the grass grow under our feet.'

The pair were taken to hospital after they collapsed inside The Maltings shopping centre after coming into contact with an unknown substance. Pictured, emergency crews at the centre

Last night police shut down a Zizzi Restaurant in Salisbury 'as a precaution' in connection with the incident

Skripal, who lives in a £350,000 house in Salisbury, is thought to have suffered a double family tragedy after his son was killed in a car crash in Russia last year - five years after his wife suffered the same fate and was buried in Britain.

As police experts desperately attempt to find out what substance Mr Skripal was exposed to, authorities have urged anyone who feels ill to contact 111 .

Last night, police shut down a branch of the Italian restaurant chain Zizzi in the cathedral city 'as a precaution' in connection with the incident, suggesting one or both of them may have dined there before.

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They also closed Salisbury Hospital's A&E unit to protect other patients and sealed off part of the city centre.

Mr Skripal was previously known for allegedly receiving £78,000 in exchange for taking huge risks to pass classified information to MI6.

Defence Secretary Mr Williamson yesterday called for the UK to wake up to the threat posed by Russia.

He warned that the Kremlin had developed a much more aggressive posture towards the UK in the past 12 months and the country should not sit submissively by.

With relations between Britain and Russia believed to be at an all-time low, Mr Williamson told MPs that the country needed to 'match what Putin is doing with Russian forces'.

During defence questions in the Commons, he said: 'Putin has made it quite clear that he has hostile intent towards this country.

'We've been seeing the build-up of his forces across the Eastern Front and in terms of what they're doing over many years now – we have to wake up to that threat and we have to respond to it.

'And it is not just through nuclear weapons – our continuous at-sea nuclear deterrent is absolutely integral to maintaining the peace, but it is also through conventional armed forces. We have to match what Putin is doing with Russian forces.'

His comments came after he was asked by Labour's Barry Sheerman about comments the Russian president had made in a state-of-the-nation speech last week.

Mr Sheerman pointed out that Mr Putin had basically announced 'a new Cold War'.

Mr Putin boasted in his speech that Russia had developed an arsenal of invincible nuclear weapons that are immune to enemy detection.

On Sunday, emergency services had said they suspected fentanyl, a synthetic opiate up to 100 times more potent than heroin, may have been involved, the Salisbury Journal reports.

A spokesman for Public Health England (PHE) said anyone exposed to the unknown substance had been decontaminated 'as is standard practice in situations like this'.

He added: 'Scientists from PHE's Centre for Radiation, Chemical and Environmental Hazards, will continue to assist the response and review information as it becomes available.'

Chairman of the Commons defence committee Julian Lewis (left) told MailOnline a proven second case of assassination on British soil would prove Russia had learned nothing from outrage at the Litvinenko murder, while Labour's Chris Bryant (right) called for a Government statement

Yesterday, Constable Holden said: 'Yesterday afternoon, at approximately 4.15pm, Wiltshire Police received a call from a member of the public who was concerned for the welfare of two people.

'The two people - a man aged in his 60s and a woman aged in her 30s - were found unconscious on a bench in The Maltings in Salisbury.

'Police officers, as well as colleagues from the ambulance and fire services, attended the scene and cordons were put in place.

'The pair, who we believe are known to each other, did not have any visible injuries and were taken to Salisbury District Hospital.

'They are currently being treated for suspected exposure to an unknown substance. Both are currently in a critical condition in intensive care.

'Because we are still at the very early stages of the investigation, we are unable to ascertain whether or not a crime has taken place.

'A major incident has been declared today and a multi-agency response has been co-ordinated.

'Alongside our partner agencies, we are conducting some extensive inquiries to determine exactly what led to these two people falling unconscious and clarify whether or not any criminal activity has happened.