MILAN, April 18 (Reuters) - Italy's communications authority (AGCOM) said on Tuesday France's Vivendi had one year to cut its stake in either Telecom Italia or broadcaster Mediaset to comply with Italian antitrust regulations.
It added that the French media group needed to present the watchdog with a "specific plan of action" within 60 days.
AGCOM opened an investigation into the French media company on December 21, after Mediaset filed a complaint over Vivendi's rapid accumulation of a 28.8 percent stake.
The regulator has looked into Vivendi's shareholdings, which also include a 24 percent share in former phone monopolist Telecom Italia.
Italian regulations prevent companies from having an excessive share in both the domestic telecommunications and media markets.
Reporting by Giulia Segreti and Stephen Jewkes