"If (the EU) won't listen to us, we will propose a referendum on the euro to ask the Italian citizens what they want to do," Maio told CNBC on Thursday.
"Those who brought us in the euro never asked us if we did want to join it. Now we ask the citizens if they want to stay in the common currency or begin to address a two-tier euro scenario or a return to monetary sovereignty," Maio said.
This Sunday's referendum in Italy could be the beginning of the end for the current government and spark fresh elections. Prime Minister Matteo Renzi decided to take a proposal to reform the constitution to a referendum vote, adding that if voters rejected it, he would resign from the government.
Polls have indicated that Italians will say "No" to the reforms and with that a "No" also to the prime minister.
A big "No" victory would mean that an early election would be inevitable.
"We are against any other government, formed by technocrats or in any other way. We are in favor of new election," Maio told CNBC.
Renzi took office in 2014, replacing the previous center-left prime minister.
"This is a prime minister who must pass through the popular vote, sooner or later," Maio added.
New elections could open the door to the 5SM. Polls have the populist party five percentage points behind Renzi's Democratic Party, which could become thinner with a referendum loss for Renzi.