MILAN (Reuters) - Mediaset (MS.MI) said on Tuesday it risked being paralysed by Vivendi's (VIV.PA) aggressive stake-building, as the French media group has accumulated a quarter of the Italian broadcaster's shares in just over a week.
Since revealing a 3 percent stake in Mediaset last week, Vivendi has rapidly tightened its grip on the Milan-based TV company, becoming the group's second biggest investor after former Prime Minister Silvio Berlusconi's family.
On Tuesday the French giant, led by Vincent Bollore, said it owned 25.75 percent of Mediaset's share capital and 26.77 percent of the voting rights.
Under Italian market rules, Vivendi would be required to launch a mandatory takeover offer for Mediaset if it reached a 30 percent shareholding. Vivendi denied on Saturday it was planning to take over Mediaset.
The Italian private broadcaster said on Tuesday it would take all measures to protect its assets, including filing a complaint with the country's communications authority over Vivendi's "illegitimate conduct and its possible obstacle to Mediaset's development strategies".
It would ask the authority to adopt "provisional and urgent measures," it said.
"There is a risk of paralysis in the industrial development activities of Mediaset as a result of the presence of Vivendi with a stake of more than 10 percent," it added in a statement.
Vivendi's recent moves have angered Italy's government and escalated a spat between the two groups, started over a soured pay-TV deal.
Officials are concerned that Bollore, who has a stake of just under 25 percent in Telecom Italia (TLIT.MI) and is a key shareholder in Mediobanca (MDBI.MI), could end up wielding even greater influence over Italy's corporate landscape.
"The corporate governance of Mediaset is proportional, so Vivendi increasing its stake could gain leverage in the Italian company," said a note by Mediobanca Securities.
But it added that a hostile takeover was unlikely.
Berlusconi's family holding, Fininvest, which owns a 38.3 percent stake, is mounting a legal battle against Vivendi, given that it cannot raise its stake further unless it intends to make a full acquisition offer.
On Monday Fininvest filed a market abuse complaint with national market authority Consob and last week it lodged a criminal complaint of market manipulation. Italian prosecutors have already started preliminary investigations.
Mediaset shares have doubled in value in December, fuelled by Vivendi's share building, putting them on course for their biggest monthly gain in their 20-year listing.
More than 10 percent of the group's shares were traded on the market on Tuesday, according to Reuters data.
Reporting by Giulia Segreti, additional reporting by Danilo Masoni in Milan; editing by Francesca Landini and Adrian Croft