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Despite facing what is effectively a vote of confidence in his leadership come October when a referendum on constitutional reform is due to take place, Italian Prime Minister Matteo Renzi told CNBC that he was sure of a win.

"I am sure we (will) win," Renzi told CNBC in an exclusive interview in Rome on Monday.

"This referendum is about the future of the country and I am sure the Italian people, if (they) read the question in the ballot in the electoral place, will vote for change," he said.

Voters will go to the polls in October to make the final decision on whether they approve constitutional reforms long championed by Renzi, including a plan to strip the upper chamber of parliament, the Senate, of most of its power and radically cuts its numbers.

The vote is potentially very destabilizing as Renzi has pledged to resign if the public votes "no." The prime minister was keen to distance the vote from being about his leadership, however.

"Our strategy in the next weeks will be (to promote the fact that) this is not Renzi's referendum. This is a referendum," he said.

Asked if he would resign if he lost the vote, Renzi would not answer the question directly and was adamant of victory, repeating "I will win."

Renzi might appear confident but as recent history has proved in the U.K., public opinion and referendum results can be hard to predict. As with the U.K.'s referendum on membership of the European Union (EU) that was held in June, Italy's referendum is also seen as close run with many voters undecided.

Political risk consultancy Eurasia Group puts a 60 percent probability on the Italian referendum passing. However, it says polls have narrowed sharply since April, making a no vote more likely as the government's popularity wanes.

A no vote would likely cause the Renzi government to collapse, according to Eurasia.

"A debilitated Renzi would come under intense pressure to resign; he may himself not wish to cling on to power," analysts Federico Santi and Mujtaba Rahman said on Friday in a report.

Aside from the referendum, Renzi is facing another serious challenge on the political front with the rise in popularity of the anti-establishment Five Star Movement.

The Five Star Movement is critical of EU institutions – as are many of the populist parties propagating across Europe – and poses a challenge to Renzi's Democratic Party, scoring a major victory Party in June when it won mayoral elections in Rome and Turin – results which Renzi played down.