The Crown Prosecution Service said Wednesday that Alexander Petrov and Ruslan Boshirov are accused in absentia of conspiracy to murder, attempted murder and use of the nerve agent Novichok.
British Prime Minister Theresa May later said that U.K. officials had concluded that the men work for Russia's GRU military intelligence agency. The Kremlin has denied involvement in the case, but May said Russia was spreading "lies."
The U.K. will not ask Moscow to extradite the men because Russian law forbids the extradition of the country's citizens, prosecutor Sue Hemming told reporters.
Skripal is a former colonel in Russian military intelligence who betrayed dozens of agents to Britain's MI6 foreign spy service. He was found unconscious on a public bench along with his daughter in the English city of Salisbury on March 4.
Police say the men, who are both aged about 40, flew from Moscow to London on Russian passports two days before the Skripals were poisoned.
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Assistant Police Commissioner Neil Basu said the men were probably using aliases.
Speaking before May's comments, Basu would not say whether police believe the suspects worked for Russian security services but described the incident as "a sophisticated attack across borders."
As a result, Basu said, police are not yet ready to press charges in the second poisoning.
Britain has issued a European Arrest Warrant for the suspects, meaning they can be detained if they leave Russia for another European country, but Basu conceded it was "very very unlikely" police would be in a position to arrest them any time soon.