President Recep Tayyip Erdogan has again called for a referendum on changing Turkey's political system to one where the president has executive powers, a day after an opposition party withdrew from a parliamentary committee tasked with drafting a new constitution.

The main opposition party pulled out of the committee on Tuesday, refusing to consider the ruling party's proposal for a presidential system, which it fears would concentrate too much power in Erdogan's hands.

The party's departure left the future of the committee in confusion.

Prime Minister Ahmet Davutoglu on Wednesday called on all parties to resume efforts to draft the new charter while his party suggested those efforts could continue without the main opposition party.

Erdogan says that the people should decide on a presidential system in a referendum.