The Skripals were poisoned by the Russian nerve agent Novichok, and while neither of them died, a British woman was later fatally exposed to the nerve agent.
The second man accused of being behind the nerve agent poisoning of Sergei Skripal has been identified as a Russian military doctor employed by the GRU, the Russian military intelligence service.
The full report, presented by two Bellingcat reporters at Westminster on Tuesday, explained how they had pieced together evidence of the man's identity from scraps of information on the internet, via leaked official databases and using a copy of personal documents, including passport dossiers.
Bellingcat said it worked with a Russian partner, the Insider, which was founded by Russian journalist and political activist Roman Dobrokhotov.
The man is believed to have traveled to Ukraine on multiple occasions, including during the Maidan events in December 2013, also under the alias of Alexander Petrov, used during his Salisbury mission.
Putin's outburst comes as the real identity of the second Russian hitman sent to kill Skripal with deadly nerve agent was revealed by investigative website Bellingcat.
Bellingcat said he made multiple trips to Ukraine.
According to a new report released by Bellingcat, Dr Alexander Yevgenyevich Mishkin was handed a Hero of Russian Federation award in late 2014 for his service in Ukraine, where Mr Putin's troops are accused of backing pro-Moscow rebels fighting government forces.
The GRU has come under the spotlight after its agents was accused of trying to hack the global chemical weapons watchdog investigating the Salisbury attack.
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Mr Grozev said that while Mishkin a had a "very sparse digital footprint" compared to Chepiga they had been able to piece together his identity using various databases, including telephone and auto insurance records.
The 39-year-old graduated from one of Russia's elite Military Medical Academies, the group's website said.
Bellingcat said Chepiga was decorated in 2014 with the nation's top award in a secret ceremony at the Kremlin.
Curiously, Mishkin's cover identity retained a lot of his authentic biography, including his real birth-date, his first and patronymic names, and the first names of his parents.
A spokesman for the Home Office said "we are not commenting as this is still a police investigation".
Following the poisoning, both Sergei Skripal and his daughter Yulia spent several weeks in a hospital, but both ultimately survived.
Higgins noted that Mishkin's home village is snowbound for much of the year. Security services in the Netherlands also published extensive materials on the operation targeting the OPCW, releasing pictures of the alleged agents and their equipment. Last week the U.S. Department of Justice indicted seven named GRU officers on charges they had hacked worldwide organizations, including the Organization for the Prohibition of Chemical Weapons (OPCW).
Russia's foreign minister Sergey Lavrov has dismissed the allegations, saying the men who were expelled from Holland had been there on a "routine" assignment to provide cybersecurity support for Russia's embassy.