Nikita Belykh, leader of the Union of Right Forces, earlier said Vladimir Putin should be removed from the ruling United Russia party's list of candidates for the State Duma, Russia's lower house, for "repeated violations of the law."
Vladimir Putin tops United Russia's list of candidates for the December 2 parliamentary elections. Critics accuse the president of using administrative resources to promote the party.
Belykh said the Kremlin had "used all opportunities provided by the state machinery" to lessen the chances of other parties.
Latest opinion surveys put United Russia in the lead for next month's elections, with some 57-59% of the vote. The Communist Party and the nationalist Liberal Democratic Party are the other two parties expected to make it into parliament, enjoying up to 9% and 7% of support respectively. No other parties are expected to overcome the 7% threshold.
Putin, credited in Russia for bringing stability and presiding over economic growth, has repeatedly rejected suggestions that he may run for a third consecutive presidential term in the March 2008 elections, amending the Constitution to this end.
However, political commentators continue to discuss possible loopholes that would allow the current president to run without violating the Russian Constitution.