The opposition lawmakers chanted slogans and jumped into the well of the main chamber as soon as the parliament opened, though three hours behind schedule.
"Announce a constitution based on consensus," the protesting lawmakers chanted.
They even overpowered and stopped Nepali Congress chief whip Chin Kaji Shrestha when he headed towards the main well to read out proposals to constitute a Questionnaire Committee as part of the process to draft a new constitution.
The ruling and opposition alliances are sharply divided on key issues in the Constitution drafting including federal structure and forms of governance.
Opposition parties' also demand ethnic identity-based federal structure in the new constitution which was supposed to be promulgated by January 22.
A brawl in the Constituent Assembly on Tuesday had left 14 people, including two senior lawmakers, injured.
Parliament Speaker Subhash Nembang today asked lawmakers to end their protests and urged them to secure an agreement or be prepared for a vote, before adjourning the assembly until Sunday.
The ruling alliance have the two-third parliamentary majority they need to approve a constitution without the opposition's support.
But the former Maoists have threatened of further conflict if they fail to take opposition views into account.
The Joint Madhesi Front, meanwhile, has called a meeting of seven Madhes-based parties tomorrow to chalk out their strategy for Sunday's CA session.
Last night, Nembang called emergency talks to resolve the contentious issues. However, an agreement could not be reached and the meeting was adjourned.
The effort by Madhesi leader Vijaya Kumar Gachhadar to find a middle path to resolve the key issues also did not succeed after Maoist chief Prachanda rejected the move.