Bellingcat named him as Alexander Yevgenyevich Mishkin, 39, who was charged by Britain last month under the name of Alexander Petrov.
The Skripals were found unconscious on March 4 on a bench in the southern English town of Salisbury.
Last month, Bellingcat named the first suspect as Anatoliy Chepiga, a claim also rejected by Russian Federation.
He was recruited by GRU during his studies at one of Russia's military medical academies, and between 2011 and 2018 he traveled repeatedly under the identity of Alexander Petrov, including to Ukraine and Moldova's breakaway territory of Transdniestria.
The Kremlin has rejected past charges about its involvement in the case as fabrications aimed at discrediting Russian Federation.
The UK in early September accused two Russian men, Alexander Petrov and Ruslan Boshirov, of attempting to assassinate ex-spy Sergei Skripal with a military-grade nerve agent in Salisbury, England in March 2018.
Bellingcat said Chepiga was decorated in 2014 with the nation's top award in a secret ceremony at the Kremlin.
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Bellingcat said its "identification process included multiple open sources, testimony from people familiar with the person, as well as copies of personally identifying documents, including a scanned copy of his passport".
He graduated from the Military Medical Academy in Russian Federation and was probably a colonel or lieutenant colonel when Skripal and his daughter were poisoned.
London police force said it will not comment on speculation regarding the real identities of the men charged with poisoning of the Skripals.
Ruslan Boshirov and Alexander Petrov give an interview to the RT news channel.
Both suspects appeared on Russian state TV last month, proclaiming their innocence.
Russia has denied any involvement in the case and has claimed the two Russians were in Salisbury on a tourist trip. They said they went to the city to visit its cathedral.
"He is just a scumbag", Putin said of Skripal.
This is how British authorities discovered the two Russian agents allegedly behind the novichok attack.