The three parties -- Nepal Congress, CPN-UML and UCPN- Maoist -- formed a three-member committee to hold dialogue with the parties and groups agitating against the new Constitution.
Nepali Congress leader and Forest Minister Mahesh Acharya and CPN-UML Chief whip Agni Kharel were named in the committee. The third member was to be named later from the UCPN (Maoist) party.
The committee was formed at a meeting of senior leaders at Prime Minister's office in Baluwatar.
"We have not been able to identify the demands or the problems they have with the new Constitution. This committee will address those reservations," he said.
Nepali Congress senior leader Sher Bahadur Deuba hoped the committee will fulfil its mandate of holding talks and resolving the current volatile situation of the country.
Meanwhile, the Nepal Army said its personnel mobilised to riot-hit areas in southern Nepal districts at the request of the local administration have returned to the barracks.
Madhesis are Indian-origin inhabitants of the Terai plains bordering India.
At least 40 people have died in over a month of clashes between police and protesters from the Madhesi and Tharu communities and ethnic minorities who say the new internal borders leave them under-represented in the country's Parliament.
Last week, India had asked Nepal to address the underlying causes of the continuing unrest "credibly and effectively".
