The only member of Russia's parliament who voted against the annexation of Crimea from Ukraine last year was formally charged on Wednesday with embezzlement in a case he has described as politically motivated.
The federal Investigative Committee, which reports to President Vladimir Putin, said a state-funded technological foundation had paid Ilya Ponomaryov $750,000 for lectures, but he had delivered only brief comments.
Ponomaryov, 39, is now in the United States and was stripped of his parliamentary immunity from prosecution in April.
Ponomaryov was alone in the 450-seat State Duma in voting against the annexation of Crimea from Ukraine last year after Russia had taken control of the Black Sea peninsula.
He says Russian authorities have prevented him returning home since August, when he went to the United States on a business trip, and have blocked his bank accounts.
While in the United States, Ponomaryov has campaigned for extending Washington's sanctions imposed over Moscow's role in the turmoil in Ukraine to include more Russian state officials.
The committee said on Wednesday that it may put Ponomaryov on an international wanted list if he fails to turn up for the investigation.