ROME, June 29 (Reuters) - Italy"s co-ruling 5-Star Movement was thrown into turmoil on Tuesday after its founder Beppe Grillo said the man primed to become its next leader, former Prime Minister Giuseppe Conte, was not up to the job. "Conte ... has neither political vision nor managerial skills. He has no experience of organisations and no capacity for innovation," Grillo wrote in a blog that looked certain to doom the ex-premier"s efforts to revive the divided group. Conte agreed to take the reins of 5-Star after his coalition government collapsed in February, but his plans to relaunch the struggling party have been delayed by internal disputes, triggered in part by his demand that Grillo relinquish control. An increasingly exasperated Conte set out his conditions for taking charge on Monday, saying Grillo had to decide whether to be a "generous father who lets his child grow up or a bullying father who prevents his child"s emancipation". Within 24 hours Grillo hit back, saying Conte wanted to subvert the maverick, anti-system nature of the 5-Star. "We cannot let a movement born to spread direct and participatory democracy turn into a one-man party governed by a seventeenth-century statute," he wrote. There was no immediate response from Conte, who was a little known lawyer with no party affiliation when he was plucked from obscurity to become head of a coalition government following inconclusive elections in 2018. He remained in charge when 5-Star switched coalition partners the following year, becoming one of Italy"s most popular leaders as his confidence grew. Many 5-Star parliamentarians had hoped that this popularity would help their own party bounce back in the polls. The group defeated all its rivals in 2018, taking 32% of the vote, but since then its image has been undermined by policy U-turns and internal feuding and it is now polling at around 16%, making it Italy"s fourth largest party. Conte had said he wanted to give the formerly anti-establishment protest movement a more traditional, moderate face as part of his efforts to form a stable alliance with the centre-left Democratic Party. read more Grillo, an outspoken comic, worried that Conte wanted to transform his group into a traditional party, peopled by slick, professional politicians.