The court rejected party incumbent leader Vladimir Kishenin's appeal made in April after the court banned the party. "Today the resolution on liquidation of the Social Democratic Party enters into legal force," he said.
Kishenin said in April that the court's decision to ban the party was "purely political."
The Supreme Court earlier upheld the suit filed by the Russian Registration Service, which stated the party's activity was unlawful since it had failed to establish local offices with at least 500 members in the majority of Russian regions, and had refused either to dissolve or transform itself into a public organization by January 1, 2007.
Social Democratic party members said then that they had established 47 regional offices with over 500 members, while the law requires representation in the majority of the 86 constituent regions of Russia.