Italy's Grillo wants disloyal MEPs to pay hefty fine

They were selected through an online ballot, restricted to party members registered before July 2013.

Dario Tamburrano, a 43-year-old dentist from Rome who supports anti-consumerist degrowth economic theory, was the most popular nominee, with 1,880 votes.

His priority, he said in a presentation video on YouTube, is to scrap austerity rules, so that leaving the eurozone would no longer "become an absolute necessity for Italy and other European countries, but remain just an option".

According to current polls, some 25 M5S candidates could make it to the EU assembly in the May elections.

Once in office, Grillo said they would be forced to resign if found in "serious breach" of the party's code of conduct, which includes an obligation to hire staff vetted by Grillo's political side-kick, Gianroberto Casaleggio, or if criminally convicted.

Failing that, they would be asked to pay the €250,000 penalty, which would be devolved to charity.

It would be up to party activists, through online voting procedures modelled on the US recall system, to demand the resignation of offending MEPs.

Giorgio Sorial, a national M5S lawmaker, defended the controversial initiative as "a way to prevent people who get to that place [the European Parliament] from being corrupted by money, forcing them to keep their feet on the ground and to listen to the voice of the citizens".

However, it is unclear how the rules could be enforced, given that under Italy's constitution elected politicians enjoy a free mandate, protecting their right to break from their party ranks if and whenever they see fit.

The M5S's Europe manifesto calls for a referendum on Italy's continued euro membership, the abolition of the fiscal compact and other euro austerity straightjackets, as well as the introduction of eurobonds and preferential treatment for domestic produce over imported food.

In the Italian parliament, the M5S has suffered from several defections by deputies and senators who have denounced Grillo's autocratic and uncompromising style.

Despite those setbacks, the 65-year-old maverick remains the biggest rival for the ruling centre-left Democratic Party (PD) of Prime Minister Matteo Renzi.

"If you are not intelligent, honest and democratic, vote for him," Grillo said of the premier, during one of the fundraising rallies he is holding in theatres up and down the country, attracting large crowds that pay entrance tickets of up to €30 each.

On Friday, the Ixe polling institute said support for both the PD and the M5S, at 32.8 and 25.5 percent respectively, was rising, while the conservative Forza Italia of scandal-prone former premier Silvio Berlusconi was bleeding support, at 16.9 percent.