Rome: The people of Italy on Sunday are required to vote in a referendum on whether or not the country should amend its 1948 constitution, the media reported.
Italian Prime Minister Matteo Renzi has called the referendum which is being closely watched for further signs of anti-establishment sentiment in Europe.
The referendum is on plans to streamline Parliament but is expected to be used by many to register discontent, BBC reported.
PM Matteo Renzi, has dramatically reduced the power of the Senate by cutting its numbers from 315 to 100 in the upper house of Parliament, CNN reported.
Renzi has said that he will resign if he loses, while Populist parties have campaigned for a "no" vote.
Opinion polls have suggested that he faces defeat.
The rise of the anti-immigrant Front National in France and populist parties elsewhere, a "no" vote for Renzi would follow Britain's vote in June to leave the European Union (EU).
Anti-establishment Five Star Movement, led by comedian-turned-politician Beppe Grillo, has attacked the “no” campaign in Italy.
Grillo has capitalised on widespread disaffection with the status of existing affairs.
His movement, founded in 2009, now appears to garner almost as much support as Renzi's centre-left Partito Democratico.
Observers fear if Grillo comes to power in an early election, he would call a referendum to scrap the Euro and perhaps even follow Britain out of the EU.
Opponents say reducing the power of the Senate would concentrate too much power in the Prime Minister's hands.
Some 50 million Italians have the right to vote in the referendum.
An opinion poll in November gave the "no" vote a lead of at least five percentage points. But many Italians are thought to be still undecided.
If Renzi loses, it is still not entirely certain that he would be out of power.
Italian President Sergio Mattarella could ask him to form a new government or appoint a technocratic prime minister to serve until elections due in 2018.
Voting begins on Sunday at 7 a.m. and ends at 11 p.m. with results expected early on Monday.