Poklonskaya signed the request to brand the Mejlis "an extremist organization" on February 15, Russian news agencies reported, RFE/RL said.
Established in 1991 and legalized by the Ukrainian government in 1999, the Mejlis has been known as an organ that addressed issues related to Crimean Tatars to Kyiv and international bodies.
The majority of Crimean Tatars opposed Russia's annexation of Crimea from Ukraine in 2014.
On February 11, Russian authorities that control Crimea arrested several Crimean Tatars on suspicion of belonging to Hizb ut-Tahrir, a Sunni political organization that is banned across Central Asia and Russia.
Crimean Tatar activists rejected the charges, saying that they were politically motivated.