The SPS ran in nine of 14 Russian constituent members where elections to local legislatures were held March 11, and managed to overcome the 7% election threshold in the Komi Republic, Stavropol Territory, Leningrad, Samara and Tomsk Regions.
Nikita Belykh said the party has documents confirming discrepancies in the vote count in the Moscow Region and "has forwarded relevant complaints to the Central Election Commission, the Moscow Election Commission, as well as the Prosecutor General's Office."
According to preliminary information, the SPS failed to overcome the 7% threshold in the Moscow Region.
"At the moment, we do not want to make any outright statements on the falsification of the election, as official results have not been made public yet," Belykh said.
He said the party also has claims against the vote count in the Omsk Region, adding that St. Petersburg was the only place where the SPS genuinely failed to overcome the 7% threshold.
The Union of Right Forces was refused registration in Dagestan, the Pskov and Vologda Regions and the Supreme Court rejected the party's complaints.
Belykh said his party will appeal to the Constitutional Court and the European Court of Human Rights, as "similar mechanisms could be used during the State Duma elections."
The regional ballots, held in 14 regions across Russia, are regarded as a dress rehearsal for elections to the State Duma, which will be held December 2, 2007.
The pro-Kremlin United Russia party won a landslide victory in 13 of the regions, trailing only the new Just Russia party in the Stavropol Territory.
The Communists (KPRF), Just Russia and the ultra-nationalist Liberal Democratic Party of Russia (LDPR) took second, third and fourth place, respectively, in most regions.
Speaking about the State Duma elections, Belykh said the SPS still hopes to unite with other democratic forces, including Yabloko.
The liberal Yabloko party, which is critical of President Vladimir Putin's policies, was barred from elections in St. Petersburg, its main stronghold.
In 2003, Yabloko won only four seats in Russia's 450-seat lower house of parliament. The party's poor performance was widely attributed to its failure to merge with the Union of Right Forces.
Belykh said the SPS will continue talks on a union with Yabloko, and has no intention of breaking up the party.
He said Yabloko has its own voters and ideology, which differs from that of the SPS, but that both parties have common democratic values.