SANTIAGO (Reuters) - The Chilean government has agreed to write a new constitution to replace one dating back to the Pinochet dictatorship, bowing to demands of protesters who have taken to the streets in often violent demonstrations in recent weeks.

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Interior Minister Gonzalo Blumel said the president, cabinet members and political allies had agreed Congress should lead the process of re-writing the constitution. The document would be put to a public referendum.

“Above all, we must focus on the goal of reconfiguring the social contract, which has arisen as a fundamental demand of our citizens,” Blumel told a news conference on Sunday night.

The announcement from President Sebastian Pinera’s center-right government follows three weeks of protests sparked by a hike in metro fares.

The demonstrations have sometimes devolved into arson, riots and looting, leaving at least 20 dead and wreaking billions of dollars in damages to public infrastructure and private business. Santiago’s public transport system has been hobbled.

A new constitution has repeatedly arisen as a central demand of protesters. Critics have long said the existing document, written and approved during General Augusto Pinochet’s 1973-1990 military dictatorship, lacks legitimacy.

Chile’s communist party said in a statement the Pinera administration had still not gone far enough, demanding a referendum even before the process begins so the “people can determine the mechanism for drafting the new Constitution.”

On Monday, Pinera’s spokeswoman Karla Rubilar held firm on the importance of routing the process through lawmakers.

“We believe firmly that the best deal will be achieved by going through Congress,” Rubilar said, adding that the administration recognized the importance of “active participation” of Chileans.

Chile’s constitution has been tweaked several times since it was enacted in 1980. But those calling for change say any new text must add further protection of social rights and increase citizen participation in the 30-year old democracy.

Opponents of the overhaul say the current charter has been a pillar of stability for Chile, among the region’s strongest and most investor-friendly economies.

Blumel did not give a timeline for the process but said the government would move quickly to begin.

“The best way to proceed is via Congress, with participation from citizens, and then, to submit it to a plebiscite,” Blumel said.