Leader of the Five Star Movement and comedian Beppe Grillo. REUTERS/Remo Casilli Beppe Grillo, the leader of Italy's populist Five Star Movement, has launched a petition to allow Italy to "leave the euro as soon as possible."

Grillo rose to prominence as a comedian and actor but since 2009 he has transformed himself into the charismatic leader of a protest movement that has seen its support growing across Italy. His sharp criticism of German-led policies that have pushed harsh austerity onto struggling Southern European economies and push for Italy to abandon the euro have seen him dubbed 'the most dangerous man in Europe' in the German press.

As testament to its growing popularity the party came third in last year's general election taking 25% of the vote and followed this with a second place finish in the European Parliament elections in May with 21.6%. Now Grillo is looking to harness his popularity to force a referendum on Italy's future in Europe's single currency.

At a rally over the weekend he said:

Tonight we are launching a consultative referendum. We will collect half a million signatures in six months – a million signatures – and we will take our case to parliament, and this time thanks to our 150 legislators, they will have to talk to us.

Although such a referendum would not be legally binding, it poses yet another headache for Prime Minister Matteo Renzi as he attempts to implement a reform program. Renzi survived a raucous vote of confidence last week in the Italian senate over his proposals to reform Italy's labor laws that economists claim have been holding back job creation and undermining the case for investment in the country.

The reforms are seen as critical to maintaining broader Eurozone, and particularly German, support for the government with Italy's economy stalling and debt-to-GDP forecast to rise to 138% by the end of 2015. Loss of support could result in substantially higher borrowing costs, putting additional pressure on the country's already strained finances.

If Grillo is able to hit his target of a million signatures pressure will be on Renzi to respond to his demands. Any sign that he is willing to backtrack on his commitment to the reform program could trigger another round of bond market panic in the ongoing Eurozone crisis, something that European leaders will be desperate to avoid.