According to a written statement released by the party, Sanliurfa deputy Osman Baydemir, who served as mayor of southeastern Diyarbakir province between 2004 and 2014, replaced Kars deputy Ayhan Bilgen. Bilgen was remanded in custody on Jan. 31 as part of a terrorism probe in Diyarbakir.
He faces a 23-year prison sentence for the charges of being a member of an armed terrorist organization, incitement to commit crime, and violating the law on meetings and demonstrations.
The government has accused the HDP of having links to the PKK, which is listed as a terrorist organization by Turkey, the U.S. and EU.
Some HDP deputies, including party leaders Figen Yuksekdag and Selahattin Demirtas, were arrested last November after they failed to answer summons to testify as part of a counter-terrorism investigation.