* Movement now country's second most popular - polls
* Vote to pick candidates for parliament from pool of 1,400
* Candidates have little political experience
By Steve Scherer
ROME, Dec 6 (Reuters) - Italy's populist 5-Star Movement, which is likely to pose a serious threat to established parties in next year's national election, is holding an online vote to choose its candidates from a list of activists with little political experience.
The unprecedented Web vote is part of the movement's determination to steer clear of anything resembling conventional party politics, which have been discredited in the wake of a string of corruption scandals.
The movement currently has no seats in parliament and the mayor of Parma, Federico Pizzarotti, is its most visible member besides its leader, the foul-mouthed and bushy-haired comic Beppe Grillo, who has pledged not to run.
The movement, which was created just three years ago and relies extensively on the Internet to communicate, has become the country's second most popular bloc behind the centre-left, with about 20 percent support in opinion polls.
The four-day online vote, which ends on Thursday night, aims to pick candidates for parliament's 945 elected seats from a pool of 1,400 activists. The results will be announced on Friday, ahead of a national vote expected no later than March.
Compared to the publicity surrounding the primary vote for the leader of the centre-left, the poll was not making much of a splash.
"Without money, without media, and against the whole system and its watchdogs we have come this far, but without your support and your warmth, we cannot continue or get anywhere," Grillo wrote on his blog.
Grillo said those in the running included "factory workers, housewives, professionals, unemployed, small-business owners, civil servants and students ... the true soul of the country".
The candidates were asked to sign an "ethical commitment" to refuse state campaign financing and accept a salary of no more than 5,000 euros per month, less than half of what most lawmakers now earn.
Grillo lifted his movement into the national arena by railing against the corruption and waste of Italy's established parties, which he says are "dead" and led by "zombies".
He backs a referendum on Italy's membership of Europe's single currency, and says technocrat Prime Minister Mario Monti - who he calls "Rigor Montis" - imposed brutal austerity so that the state could pay back the banks that put him in power.
The selection of Democratic Party (PD) leader Pier Luigi Bersani to head the centre-left after a primary last Sunday has refreshed the party's image and boosted its support to more than 34 percent in the latest opinion poll.
PD leaders have expressed concern that the collapse of the centre-right People of Liberty (PDL) party of former premier Silvio Berlusconi will leave little credible opposition aside from the 5-Star Movement.
Berlusconi on Wednesday hinted after months of indecision that he might stand as candidate for the PDL in an attempt to reverse a slump in its popularity. PDL senators walked out of a confidence vote in the Monti government on Thursday, ratcheting up the tension in an increasingly fevered pre-election atmosphere.
While the centre-left's primary dominated the media for weeks, the movement's online poll has been treated more as a curiosity than a news story.
This appears to suit the party, either because it does not want to call attention to the inexperience of its candidates or because it wants to keep the spotlight on its flamboyant founder, who keeps party members on a tight leash.
Grillo swam the Straits of Messina to kick off the movement's campaign in a regional vote in Sicily in October, after which it became the island's single biggest party.
Party members, by contrast, cannot appear on television talk shows and Grillo lambasts on his blog any activists who express opposition to the movement's policies. (Editing by Barry Moody and Sonya Hepinstall)