THERESA May today accused Vladimir Putin of sending two military agents to Britain to carry out a hit on ex-spy Sergei Skripal.
As the two suspects in the Novichok poisoning were named for the first time, the PM revealed they are thought to be members of Russia's military intelligence service - and took a dig at Jeremy Corbyn for previously doubting Putin's role in the attack.
Mrs May said the pair - Alexander Petrov and Ruslan Boshirov - were not involved in a "rogue operation" but had the approval of Putin or his ministers.
Speaking in the Commons, the PM said: "The Government has concluded that the two individuals named by the police and CPS are officers from the Russian military intelligence service, also known as the GRU.
"The GRU is a highly disciplined organisation with a well-established chain of command.
"So this was not a rogue operation. It was almost certainly also approved outside the GRU at a senior level of the Russian state."
She also took a pair of coded digs at the Labour leader, who previously said there wasn't enough evidence to pin the blame for the Novichok assault on Russia.
Mrs May said: "I would hope some of those who previously were cautious about accepting what we had said in March about responsibility for this will now see the clear responsibility that lies at the doors of Russia and will act accordingly."
And responding to SNP boss Ian Blackford, the PM added: "Can I thank him for his clear condemnation of the Russian state - I would only hope that that condemnation would be shared by the leaders of all parties."
Senior backbenchers also attacked Mr Corbyn for his ambiguous stance on the incident.
Boris Johnson - who said the "highest level" of the Russian state was responsible - called the Labour leader "weaselly" for refusing to point the finger directly at Putin.
And Amber Rudd insisted he should have trusted British spooks' initial conclusions, saying: "When the security services lead us in this direction, they know what they are doing."
Earlier today, an arrest warrant was issued calling for Petrov and Boshirov to be detained if they step foot in Britain or any other European country.
Prosecutors want to charge the pair over the attempted murder of Sergei Skripal, and the poisoning of his daughter Yulia and police officer Nick Bailey.
Mrs May further accused the two men of being responsible for the death of Dawn Sturgess, who was taken ill in Amesbury along with her boyfriend Charlie Rowley.
The Prime Minister - who spoke to Donald Trump about the case last night - said: "Were these two suspects within our jurisdiction, there would be a clear basis in law for their arrest for murder."
And she revealed that the names of the suspects were discovered after a team of 250 detectives combed through 11,000 hours of CCTV footage and took more than 1,400 witness statements.
Mrs May took aim at the Putin regime for trying to block justice in the case - and putting out bizarre conspiracy theories designed to hide the truth.
She told MPs: "We repeatedly asked Russia to account for what happened in Salisbury in March, and they have replied with obfuscation and lies.
"This has included trying to pass the blame for this attack onto terrorists, onto our international partners, and even onto the future mother-in-law of Yulia Skripal.
"They even claimed that I, myself, invented Novichok. Their attempts to hide the truth by pushing out a deluge of disinformation simply reinforces their culpability."
Vowing to take further action against the Russian state, the PM added: "On the basis of what we have learnt in the Salisbury investigation - and what we know about this organisation more broadly - we must now step up our collective efforts, specifically against the GRU.
"We are increasing our understanding of what the GRU is doing in our countries, shining a light on their activities, exposing their methods and sharing them with our allies, just as we have done with Salisbury.
"Together with our allies, we will deploy the full range of tools from across our national security apparatus in order to counter the threat posed by the GRU."
Mrs May declined to name Putin during her statement, despite pointing the finger at his inner circle.
But several MPs went further and blamed the Russian president personally for the poisoning - Labour's Chris Bryant said in the Commons: "I do not doubt for a single second that the bloody trail goes back to the Kremlin and to President Putin personally."
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Bob Seely, a Tory MP who is an expect on Russia, added: "The order to conduct this murder probably came from only one man, Russian president Vladimir Putin."
Officials said today that Petrov and Boshirov flew in to Britain on valid Russian passports, stayed at an East London hotel and took the train to Salisbury where they were caught on CCTV near the Skripals' home.
The pair apparently disguised their deadly weapon in a bottle of perfume - which was picked up months later by Ms Sturgess, leading to her death and Mr Rowley's poisoning.
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