The Ulyanovsk regional court has upheld a fine against Sergei Udaltsov, the coordinator of Russia's Left Front opposition movement.
Earlier this year, Udaltsov was found guilty of beating up a pro-government female activist during an anti-NATO demonstration in the city of Ulyanovsk in Russia's Volga region.
A local court later ruled that Udaltsov must pay a fine of 35,000 rubles ($865).
Udaltsov filed an appeal denying wrongdoing.
Neither Udaltsov nor his lawyers were present at the Ulyanovsk court for the decision announced on November 19.
Udaltsov told journalists in Moscow that he planned to continue to appeal the decision.
According to him, the authorities fabricated the case to turn him into a man with a criminal record.
Based on reporting by Interfax and ITAR-TASS