Koirala's remarks came a day after the parliamentary party of the Unified CPN (Maoist) finalised its draft statute proposing the presidential system of governance.

Speaking at the launch of "Apurna Kranti", a book penned by Lokesh Dhakal, Koirala said he would not support the presidential system as it was detrimental for the future of the country.

In its draft statute, the Maoist party has said executive powers shall rest with the President and the Prime Minister shall have limited powers.

"To adopt the presidential system is to impose authoritarianism in the country. Any party that advocates this system will collapse," Koirala predicted. "Congress will not let the country adopt this system."

He said the new constitution must adopt the parliamentary system because political parties were familiar with it. The former prime minister argued that decentralisation of power and distribution of resources must be the bases for federalism.

"The Hill, Mountain and Tarai must not disintegrate while we decide on federalism," he said. "Federalism that disintegrates the country is unacceptable."

Koirala said sustainable peace and development cannot be achieved without promulgating the new constitution