Why a US hedge fund is taking on one of Europe's media giants

London(CNN Business) A spirited fight between a top US hedge fund and one of Europe's largest media companies is producing nothing but pain.

The latest casualty of the increasingly vitriolic quarrel between Elliott Management and French conglomerate Vivendi is Amos Genish, who was ousted on Tuesday as CEO of Telecom Italia (TI).

Vivendi and Elliott have battled over the future of Telecom Italia since March 16, when the hedge fund led by billionaire Paul Singer said it had acquired a stake in the former state monopoly. Vivendi owns 24% of the shares.

Elliott has scored a series of victories, including the ouster of Genish and board members backed by Vivendi (VIVEF). Yet shares in Telecom Italia have plunged by over 30% since March, suggesting investors are skeptical.

The hedge fund has claimed there is a "clear and overwhelming case for change" at the telecoms group.

It argued in a letter to shareholders in March that Vivendi, which is controlled by French billionaire Vincent Bolloré, had harmed smaller investors by exercising "disproportionate control" over Telecom Italia.

Elliott said the Italian company should spin off or sell part of its phone network business to reduce its debt levels and capitalize on a push into broadband. Telecom Italia has agreed to separate the network but wants to keep full ownership.

The hedge fund also wants Telecom Italia to sell part of its submarine cables business, and resume dividend payments.

Telecom Italia has 32 million mobile users, and its traditional phone network is among the strongest in Europe. Including operations in Brazil, its sales reached €14.7 billion ($16.6 billion) in the first nine months of 2018.

There are signs that the spat could get worse before it gets better.

Vivendi and Elliott traded barbs on Tuesday following the announcement that Genish would depart as CEO.

"Genish had the opportunity to create value; we supported him. In actuality, he did precisely nothing and instead proved to be an impediment to value creation," an Elliott spokesperson said in a statement.

Representatives for Vivendi did not respond to questions from CNN Business on Tuesday, but a spokesman told Reuters: "We decry, we condemn the destabilization behind this decision and the disgraceful methods. We reserve all our rights to defend all shareholders interests."

The board of Telecom Italia, where Elliott now has more loyalists than Vivendi, will meet on November 18 to select a replacement for Genish.