"If these results are confirmed, this will be a big victory for the people and Renzi will have to resign within minutes so elections can be held immediately," Salvini told a press conference.
He thanked Italians for a high turnout ans stressed that a failed referendum is a defeat for Renzi as well as his "cronies."
"We will be ready to provide an alternative to Renzi's government for all those who are ready to go and vote," he said.
Renzi previously vowed to step down if the vote is negative. Italy's anti-establishment Five Star Movement has also been campaigning against prime minister’s constitutional reforms. Opinion polls ahead of the vote indicated they have a high chance of being rejected. Renzi is soon due to give a press conference on the outcome of the vote.