Turkey's ruling Islamist-rooted AK Party tried on Friday to speed up a likely referendum on constitutional reforms that have deepened a crisis between it and the secular elite ahead of July general elections.
The main opposition Republican People's Party (CHP) said it would mount a legal challenge to the reforms, which pave the way for voters instead of parliament to elect the president.
Prime Minister Tayyip Erdogan wants to hold the referendum as soon as possible to improve the chances of an AK candidate being elected president of the EU aspirant. He says the ballot could be held on the same day as July 22 parliamentary polls.
Turkey's secular elite, which includes top judges and army generals as well as the CHP and other opposition parties, aims to stop the AK Party winning the presidency, fearing it would use the post to undermine the separation of state and religion.
Parliament, where the AK Party has a big majority, approved the constitutional reforms on a second and final reading on Thursday, overriding a veto by President Ahmet Necdet Sezer, a stern secularist critic of Erdogan's government. Sezer cannot veto them a second time and must either sign them directly into law or call a national referendum.
Under the AK Party proposal, which was debated in a parliamentary commission on Friday, the length of time before a referendum can be held would be cut to 40 days from 120 days. Senior CHP lawmaker Ali Topuz told reporters his party would ask the Constitutional Court to rule the reforms invalid on technical, procedural grounds. He said the CHP would make its legal appeal next Monday or Tuesday.
The staunchly secularist court may well uphold the appeal. Last month, it backed the CHP in another appeal that effectively derailed the government's efforts to have parliament elect Foreign Minister Abdullah Gul, an ex-Islamist, as president.
This week the head of the Constitutional Court, Tulay Tugcu, accused Erdogan of undermining the rule of law by describing that court ruling as a "disgrace". She has asked state prosecutors to investigate Erdogan's remarks.
In a possible fresh setback for Erdogan, Deputy Prime Minister Abdullatif Sener, a respected moderate who has overseen some key economic institutions, announced on Friday he would not seek re-election in next month's poll.