Prime Minister Silvio Berlusconi on Tuesday recognised a humiliating defeat in opposition-backed referendums aimed at blocking nuclear power and abolishing a law intended to give him legal immunity.
"The high turnout in the referendums shows a will on the part of citizens to participate in decisions about our future that cannot be ignored," Berlusconi said, after official data showed 57% of voters had taken part.
Turnout was of crucial importance since the referendums required participation of more than 50 percent in order to have legal force.
"The will of Italians is clear on all the subjects of this consultation. The government and parliament must now respond fully," Berlusconi added.
Final results are due later on Tuesday but early data showed crushing votes of more than 90% against the government in the four referendum questions - one on nuclear, one on the immunity law and two on water privatisation.
"Italians have finally woken up and decided to take their destiny into their hands," said a jubilant Margherita Sina, 25, one of hundreds partying in the streets of Rome as the results came in.
"This is huge. Italians have become more responsible," she said.
The setback for Berlusconi comes after the embattled premier's People of Freedom party lost mayoral elections in Milan and Naples in May - a failure that already had many commentators predicting his demise.