Italian broadcaster Mediaset and major shareholder Fininvest are claiming €3bn ($3.6bn) in damages from French media group Vivendi.
Mediaset, one of the leading sports broadcasters in Italy, is seeking damages from Vivendi after the latter stepped away from an April 2016 agreement to take full control of pay-television broadcaster Mediaset Premium.
Vivendi pulled out of the proposed €800m deal just over a year ago after claiming that Mediaset Premium's business plan was unrealistic.
The case went to court earlier this year, with both sides filing lawsuits against each other.
Since April 2016, Vivendi has accumulated a significant minority stake in Mediaset – reported to be 28.8 per cent.
Autorità per le Garanzie nelle Comunicazioni (Agcom), the Italian communications regulator, has ordered the French company to reduce its stake in Mediaset or telecommunications company Telecom Italia (TIM) by April 2018.
Vivendi last month confirmed plans to form an Italian pay-television platform in association with its TIM and Groupe Canal subsidiaries. Such a platform would compete head-on with Mediaset Premium.