In his statement, Şahin said the AKP had now been controlled by a narrow cadre, had drifted away from its founding principles and had closed all channels for self-reflection, consultation, and joint decision making, adding that there was no more any possibility of triggering a change inside the party.
"My resentment is not to my brothers and sisters within the AKP but only to non-sincere administrators,” Usta said.
Two resignations are the latest in a string of resignations from President Recep Tayyip Erdoğan’s AKP, which suffered its greatest defeat in its 17 years in power in the March local elections.
AKP lost five of Turkey’s most populous provinces to the main opposition CHP, including capital Ankara and financial-hub Istanbul.
Former Prime Minister Davutoğlu and former deputy Prime Minister Ali Babacan are among the ex-AP heavyweights who parted ways with the AKP earlier this year to establish new political movements.