Tunisia's new constitution will not be adopted by parliament until April 2013, six months later than planned, Habib Khedher, who heads the committee in charge of drafting the constitution, said on Monday, Ahram reported.
"The final draft of the constitution could be put to the vote (in the National Constituent Assembly) at the end of April," said the lawyer, who belongs to the ruling Islamist party Ennahda and is an elected member of the interim parliament.
"I think that is a realistic target," Kheder told AFP.
The government had until now insisted that it would meet the deadline of October 23 for ratifying the new constitution, in order to hold planned general elections in March 2013.
The delay risks aggravating the political uncertainties facing Tunisia, which has been rocked by social unrest in recent months linked to poor living conditions and fears that a rising Islamist tide threatens personal freedoms.
The new timetable will be discussed at a meeting of the NCA on September 3, ahead of the next parliamentary session, Kheder said.
Tunisia's main parties were given one year to draft a new constitution, after elections that brought Ennahda to power at the head of a coalition also grouping centre-left parties the Congress for the Republic and Ettakatol.
It will replace the provisional laws that have governed Tunisia since the revolution that overthrew veteran strongman Zine El Abidine Ben Ali in January 2011, and allow fresh elections to take place.
But the project has been heavily delayed due to an apparent deadlock over certain key issues, with the Islamists seeking a pure parliamentary system and the other parties wanting important powers to remain in the hands of the president.
The first version was due to have been presented at the end of last month, but was never completed, and a final draft should have been ready by October, Kheder explained.
There are six committees responsible for the six different chapters of the constitution, with each article to be submitted individually for approval by MPs, who can make further amendments.
Only then can the text be adopted by parliament, where it requires a two-thirds majority.
In the absence of compromise, the draft constitution will be put to a referendum.