The North African country's political stability remains fragile, two and a half years after the revolution that ousted veteran strongman Zine El Abidine Ben Ali, adding urgency to the need for the new charter.
But the debate was suspended after less than 30 minutes when the presentation by the head of the drafting committee, Islamist MP Habib Kheder, was interrupted by opposition MPs who accuse him of introducing controversial articles in a discretionary manner.
When Khoder finally returned to the podium to resume his presentation at around 6 pm (1700 GMT), he was again drowned out by heckling from opposition MPs who shouted slogans and sang the national anthem.
Before the session was interrupted, a handful of secular opposition MPs issued a statement criticising the "fraudulent process that has affected the workings of the constituent committees."
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"The men of Tunisia remained seated... These were dwarfs who stood up, she told private radio Mosaique FM, condemning the "immaturity in the ranks of the opposition."
Several hundred people also protested against the draft constitution outside the National Assembly, which has been repeatedly criticised for its inefficiency and the non-attendance of members.
Beyond the controversial clauses introduced, some civil society and opposition activists have raised concerns that the text does not sufficiently guarantee basic liberties.
Amnesty International said it undermined the principles of international human rights law by giving greater legal value to the constitution than to international treaties ratified by Tunis.
Ennahda had previously insisted on a pure parliamentary system before allowing the head of state to retain important powers, notably in the areas of defence and diplomacy. The Islamists also agreed to abandon having the Koran inscribed as a source of law.