Turkey's parliament has approved a draft bill that would dramatically expand the president's powers - paving the way for a referendum later this year.
The government insists the proposal to create an executive presidency will ensure more simple, more stable and more effective administration, but critics say it will give the Turkish president, Recep Tayyip Erdogan, more power that is unchecked.
Erdogan became Turkey's first president elected by popular vote in 2014, after serving three terms as prime minister. If passed, he could stay in office until 2029.
"A new door in Turkish history and in the lives of the Turkish people has been cracked open today. With our people's 'yes' vote, this door will be completely opened," Bekir Bozdag, justice minister, wrote on Twitter.
Kemal Kilicdaroglu, leader of the main opposition Republican People's Party (CHP), said after the voting that his party would fight the changes in their referendum campaign.
"This is a betrayal by the parliament of its own history. Our people will certainly thwart the game that was played in parliament ... We will go from door to door and explain this to our people," Kilicdaroglu said.
Parliament approved the 18-article constitutional change, which was submitted in December, with 339 "yes" votes. The number of MPs who voted against the bill was 142.
Since last month, each article of the bill was put to vote in the 550-seat parliament, where the ruling Justice and Development Party (AK Party) enjoys a comfortable majority with 317 seats.
At least 330 votes, a three-fifths majority, were needed to adopt the constitutional change.
The AK Party passed the bill with the support of most MPs from the Nationalist Movement Party (MHP).
The changes were also opposed by the pro-Kurdish People's Democracy Party (HDP).
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Immediately after the bill was approved, Prime Minister Binali Yildirim said the "last word" would be had by the people in a referendum, expected to be held in April.
"No one should have any doubt of this: On the issue of constitutional change, the most correct decision will certainly be given by the people," he said.
The bill would create an executive presidency for the first time in modern Turkey and give the president the power to appoint and fire ministers.
In addition, the post of prime minister will be abolished for the first time in the country's history and replaced by a vice president, or perhaps several.
The president will be allowed to issue decrees and retain ties to a political party. Also, he or she will have broad authority over the high council of judges and prosecutors.
If the changes are passed in the referendum, Turkey would head to general and presidential elections together in November 2019, and proposed powers would be granted to the president elected.
The bill indicates a person can be elected president for two, five-year terms. Erdogan's existing time as president will not be counted.
Source: Al Jazeera and news agencies