Investigative group Bellingcat on Tuesday said the second suspect in the poisoning of former Russian spy Sergei Skripal was personally decorated as a hero by President Vladimir Putin in 2014.
The site on Monday said the man, who used the alias "Alexander Petrov", was in fact Alexander Mishkin, a trained military doctor employed by Moscow's GRU military intelligence service.
Bellingcat founder Eliot Higgins and researcher Christo Grozev told reporters at an event in the British parliament on Tuesday that they found out Mishkin had taken part in undercover operations in Ukraine and the breakaway republic of Transnistria.
Higgins and Grozev also said that Mishkin took part in military operations in eastern Ukraine in 2014 and was made a Hero of the Russian Federation by Putin in autumn of the same year.
Bellingcat has previously identified GRU colonel Anatoly Chepiga as the other suspect and said that he too had received Russia's highest award in the same year in a secret ceremony in the Kremlin.
The two men are accused by British authorities of attempting to murder Skripal and his daughter Yulia with a Soviet-made nerve agent called Novichok in March in the city of Salisbury in southwest England.
The Bellingcat investigation also said that Mishkin was born in the village of Loyga in northern Russia in 1979 and graduated from the Russian military's medical academy in St Petersburg, where he specialised in "deep underwater physiology".
The researchers said that he was recruited by the GRU "at some point before 2003" and moved to Moscow in around 2009 where he adopted the identity of Alexander Petrov.