Oppositions lawmakers have warned that the state "will be degraded to one political party" under the amendments. Turkey's president threatened fresh elections if the package of amendments failed to pass in parliament.
Turkey's parliament on Friday approved a series of constitutional amendments that would allow the president to issue decrees and be a member of a political party.
With support from the Nationalist Movement Party (MHS), the ruling Justice and Development Party (AKP) pushed through the key legislative measures in support of Turkish President Recep Tayyip Erdogan's vision of a strong executive leadership.
However, the opposition, including the Republican People's Party (CHP) and pro-Kurdish People's Democratic Party (HDP), voiced concern that centralizing power in the presidency will fuel authoritarianism.
Former Foreign Minister Deniz Baykal of the CHP said the amendment to allow the president to remain a party member will prevent the "impartiality" associated with the office.
"The state will be degraded to one political party and that political party will be turned into the state's party. That is dangerous," Baykal said, according to state-run Anadolu Agency.
The 18-article bill requires two more votes in parliament, with at least 330 parliamentarians voting in favor, before it heads to a national referendum.
Under the new measures, the president would be allowed to serve two five-year terms with presidential elections under the draft legislation envisaged for 2019.
'Worst crisis in a generation'
On Friday, Erdogan warned that early elections would be held if the 18-article bill failed to pass parliament, saying it was not desired but "not unthinkable."
"Usually, those who are in power try to preserve the status quo and the opposition tries to change it," Erdogan said. "However, it has been the other way around in Turkey for a long time. Those who are in power are struggling to reform, change. And some of the opposition members are guarding the status quo."
Since a failed coup attempt in July, Turkey has witnessed a major crackdown on human rights, freedom of the press, and freedom of assembly.
Human Rights Watch has described the government's actions following the failed coup as a "ruthless crackdown on critics and opponents."
"With hundreds of thousands of people dismissed or detained without due process, and independent media silenced and Kurdish opposition members of parliament in jail, Turkey has plunged into its worst crisis in a generation," said Hugh Williamson, Human Rights Watch's Europe and Central Asia director.
ls/sms (dpa, Reuters)