KATHMANDU: Nepal risks more turmoil if it fails to address the demands for greater representation of minority ethnic Madhesis in the new constitution, the International Crisis Group (ICG) said on Tuesday in a report that drew criticism from the government.

More than 50 people have died in protests since September in the Tarai, or Madhes, a region in Nepal's southern plains bordering India, overshadowing the first post-monarchy constitution.

The charter was the final condition of a peace deal between the government and Maoist rebels, which ended a decade-long rebellion in the Himalayan nation in 2006.

But many Madhesis want the region, which is home to half of the country's 28 million people, to become an autonomous state within Nepal and not be broken up into parts of six of the seven federal provinces as envisaged in the new constitution.

The ICG said in its report the depth of social discontent, lack of fruitful negotiations and disillusion among the Madhesis with the parties that represent them was creating room for radical positions.

"Forcing acceptance of a flawed constitution could end the political transition and trigger unmanageable new conflict," the ICG, an independent non-governmental organisation, said.

Minister for Information and Communications Sherdhan Rai was critical of the report, which he said contained "unnecessary" comments. "We are ready to negotiate and address genuine demands of the Madhesis," he told Reuters.

But Upendra Yadav, from Madhesi Front which organised protests, said the government was unlikely to convene early talks. "Lasting peace and stability are impossible without addressing our demands," he said.

Several small Madhesi groups have given the government until April 12 to address their demands, warning of fresh action after a five-month border blockade caused severe fuel shortages.

Covering 23 percent of landlocked Nepal, the Tarai is the country's bread basket, providing rice, wheat, and is home to industries like jute and sugar.