Russia's liberal opposition People's Freedom Party (Parnas) appealed on Friday the Justice Ministry's refusal to register it ahead of December's parliamentary polls.
The Justice Ministry said last month some of the party's 46,000 signatures of supporters - a requirement for registration - included dead people and teenagers. The party, which brings together five previously separate opposition groups - denies the charges.
"The only four reasons to refuse to register a party are the threat of separatism, a threat to human lives and health, and degradation of political morals and the lessening of citizen rights," Parnas co-head Mikhail Kasyanov said.
Kasyanov, prime minister under Vladimir Putin's first period as president, said even if the party's court appeal was successful it would not now be able to fulfill other legal requirements necessary to take part in the polls.
The decision to refuse to register the group sparked criticism from both the U.S. and the European Union.