Alfred Kokh, a blogger and former government official, said via Facebook that he was questioned Friday, RIA Novosti reported.
"Two lieutenant colonels of the ... [Investigative Committee's] main investigation department spent three hours establishing the details of [State Duma deputy Yelena] Mizulina's gay and oral phobias and my position on them," Kokh wrote on his Facebook.
Kokh, who served as deputy prime minister, said that he will be questioned again on August 21.
Last week, Kokh said Mizulina filed a complaint against him for slander over his public criticism of her conservative policies.
Mizulina denied naming Kokh in her complaint, saying she told the Investigative Committee about unspecified critics who make slanderous statements online.