Dozens of opposition deputies walked out of Tunisia's constitutional assembly Monday to protest against the final draft of a new post-Arab Spring constitution.

The cradle of the pro-democracy uprisings that wracked the Middle East and North Africa in 2011, Tunisia has been closely watched as it works its way through a democratic transition marred by economic crisis, violence and the struggle between Islamists and secularists over the nation's identity.

The walkout by opposition deputies singing the national anthem forced parliament speaker Mustapha Ben Jaafar to close the session shortly after opening it.

Opposition deputy Nadia Chaabane accused the ruling moderate Islamist party of altering the final draft of the constitution written by the assembly's committees, prompting the walkout.

The constitutional assembly has been writing the nation's new charter since it was elected in October 2011, taking eight months longer than its allotted year as the nation's economy has suffered, provoking further social unrest.

The assembly and the government is dominated by the moderate Islamist Ennahda Party that was severely repressed by Ben Ali and now rules in coalition with two secular parties.

The opposition accuses Ennahda of trying to write a constitution that would increase the religious character of society, and the draft has already been modified three times in debates over references to Islam, the role of women and guarantees for personal freedoms.

The debate over each article of the constitution is expected to last for much of the rest of the summer, including the holy month of Ramadan, set to begin in about a week.

If the document does not pass with 2/3 support of the assembly — which would mean with some opposition backing — it will go to a public referendum.

Elections for a permanent parliament, and therefore government, were to be held in July but have been postponed to the end of 2013. They are widely expected to be further delayed to spring 2014.