Anatoly Chubais was a senior figure in Moscow who is widely known as a Russian liberaliser. Some claim he was responsible for giving Putin his first role in the Kremlin in the mid-1990s.
Chubais was last year appointed special Presidential envoy for sustainable development.
But after Putin announced his “special military operation” in Ukraine earlier this year, Chubais was reported to have stood down from his role and left the country.
Concerns were then raised when earlier this week he was said to have been admitted to a hospital in Europe.
Commentators were quick to speculate that Chubais had been poisoned due to his act of opposition.
More details have today been released on his condition, as well as the first two photos of Chubais in a hospital bed.
Russian television host and actress Ksenia Sobchak shared information to her 1.2million Telegram subscribers.
She said: “Anatoly Borisovich Chubais finally confirmed the diagnosis: Guillain-Barré syndrome.
“His condition has stabilised, but Anatoly Borisovich is still in intensive care, his legs and arms do not work well, his eyes cannot be closed, he has partial facial paralysis.”
The pundit also shared two photos of the former Putin ally.
She wrote alongside these: “The first photo of Anatoly Chubais after hospitalisation. This is how he looks right now.”
Sobchak did not comment on the suggestion Chubais has been poisoned.
One source, speaking on the condition of anonymity, recently told Reuters: “I don’t think it is poisoning.”
Another added: “He [Chubais] thinks it’s a disease.
“Doctors say they found it in time.”