A top official at the pro-Kremlin United Russia party, Andrei Vorobyov, resigned following a vote by the party on Saturday.
"Today is my last day as chairman of United Russia's central executive committee. It's been almost seven years!" Vorobyov, a close ally of Prime Minister Vladimir Putin and leader of the party's faction in the lower house, wrote on his Twitter account.
He has held the post since 2005.
Konstantin Mazurevsky, leader of United Russia's youth wing, was appointed caretaker, the daily Izvestia reported.
Vorobyov earlier said he would resign as chairman of the party's executive committee after presidential elections next month.
The 42-year-old is the second key United Russia offical to step down in recent months, following the resignation of Boris Gryzlov, the party's chairman, as State Duma speaker in December.
Andrei Isayev, a senior party official, said Vorobyov's resignation had been "in the pipeline for a long time."
"It has been decided that he should concentrate on his work as faction head," Isayev told the Russkaya Sluzhba Novostei radio station.
Claims of fraud in favor of United Russia at December’s parliamentary polls have sparked the biggest anti-government protests seen in Russia in decades.
