The second suspect in the Salisbury poisoning case was a doctor and highly decorated Russian military intelligence officer, an investigative website says.
Bellingcat said it used a combination of online material and leaked documents to identify Alexander Mishkin, 39, as someone linked to the attack in March.
It said President Vladimir Putin had presented him with the Hero of the Russian Federation award.
When asked about the naming of Mr Mishkin, the Kremlin would not comment.
Last month, Bellingcat named the first suspect as Anatoliy Chepiga, a claim also rejected by Russia.
At a news conference in the Houses of Parliament on Tuesday, Bellingcat investigator Cristo Grozev said Mr Mishkin – like Mr Chepiga – was a member of the GRU and given the celebrated award in the autumn of 2014 for “actions in Ukraine”.
The BBC has contacted two people who knew Mr Mishkin as a child in a village of Loyga in the north of Russia, who confirmed from photographs that he is the man seen in images released by police after the Salisbury attack in March.
Former GRU officer Sergei Skripal – who sold secrets to MI6 – and his daughter Yulia survived being poisoned with Novichok on 4 March.