By Gavin Jones
ROME (Reuters) - Italy's anti-establishment 5-Star Movement on Thursday lost five more senators who were critical of its leader Beppe Grillo in the latest sign of growing internal strife in the party that took a quarter of votes at last year's election.
Grillo announced on his blog that the five senators were "out of the movement" having handed in their resignations to senate president Piero Grasso.
Polls suggest 5-Star has kept most of its support despite growing dissent among lawmakers unhappy with Grillo, a fiery comedian who rode a wave of public disgust with traditional parties to create a powerful political force.
The 5-Star Movement commands around 20-22 percent of the vote, according to most opinion polls, down from the roughly 25 percent it won at the February 2013 election. It still ranks as the third biggest party in terms of seats in parliament.
However, what began as a trickle of defections among its parliamentarians has gathered speed, raising questions about the future of the movement that elected scores of young lawmakers with no previous political experience.
The party is split between a majority of loyalists and a growing minority of dissidents unhappy with Grillo's autocratic methods and political strategy of hardline opposition.
Of the 54 senators and 109 lower house deputies elected by 5-Star in February last year, 13 senators and three deputies have now left or been expelled.
The latest five senators to go, Alessandra Bencini, Laura Bignami, Monica Casaletto, Maria Mussini and Maurizio Romani had said they were unhappy with the party's expulsion of four other senators just last month.
Francesco Campanella, one of the four senators expelled in February, said on Thursday that Grillo considered himself the "owner" of the 5-Star Movement.
"It was partly thanks to him that this movement was wonderful but now he has decided to destroy it," he said.
The catalyst for the most recent divisions was criticism by party moderates of Grillo in his dealings with new Prime Minister Matteo Renzi.
In a brief meeting with Renzi last month, broadcast online, Grillo used the opportunity to attack the prime minister rather than seek common ground as the dissidents would have preferred.
Renzi, who heads a fragile left-right coalition, is likely to welcome any signs of a 5-Star split. He has repeatedly appealed to the movement's parliamentarians to reject the uncompromising opposition dictated by Grillo and to collaborate with his government.
(Editing by Angus MacSwan)