The leader of the regionalist Northern League, Umberto Bossi, is coming under pressure to pull out of the government after the referendum defeat, which followed the loss of the key city council of Milan in local elections two weeks ago.
"In the local elections two weeks ago we took the first hit. Now, with the referendum, has come the second. I would not like taking hits to become a habit," said Northern League member and cabinet minister Roberto Calderoli.
"We shall probably have to say goodbye to nuclear [energy]," Berlusconi conceded on Monday as the landslide against his plans became clear.
Shares in renewable energy company Enel Green Power rose 1.41 per cent on the Milan stock exchange.
With public concern high in the aftermath of Japan’s Fukushima power station accident, government supporters who feared their regions would be picked as sites for nuclear power stations voted “no”, contributing to a 94.1 per cent rejection.
Berlusconi himself did not vote and his supporters called on Italians not to cast their ballots in an attempt to keep turnout below the 50 per cent needed to give the results legal force.
But turnout was 57 per cent and the rejection of the water privatisation and immunity proposals were even higher than the nuclear power plan at 95.8 per cent and 94.6 per cent respectively.