PARIS, July 28 (Reuters) - Vivendi's top investor, billionaire Vincent Bollore, is weighing the sale of the group's publishing unit Editis to avoid antitrust hurdles as it seeks to take over French media group Lagardere.

The Vivendi-Lagardere tie-up, which is being reviewed by the European Union's antitrust authorities, would create a new publishing behemoth through the combination of France's two biggest publishing groups, Lagardere's Hachette and Vivendi's Editis.

That prospect has triggered a wave of criticism from independent publishers in France, including the most famous one, Gallimard. Several best-selling French authors also have left Hachette.

"We knew that there would be some (competition) hurdles," Vivendi's CEO Arnaud de Puyfontaine said in a call with investors.

"We wanted the remedy to be the best one for all the stakeholders," he added, referring to the potential sale of Editis.

Vivendi did not disclose details on the valuation of Editis and a timeline for the would-be disposal.

Under the plan, Bollore would sell all the Editis shares he would receive after the transaction, which would consist of a simultaneous distribution of Editis shares to Vivendi shareholders and the listing of Editis on the Euronext Paris stock exchange, it said.

Bollore is Vivendi's controlling shareholder with a 29% stake. The mass media holding company already owns 57% of Lagardere following a bid for all of the shares of the group, which is also home to flagship news publications such as JDD and Paris Match.

Vivendi has said it is ready to spend as much as 2 billion euros to acquire all of Lagardere's shares.

But Vivendi's voting rights in Lagardere are capped at 23% until a merger approval by competition authorities.

Vivendi reported that its revenue in the first half of the year was 4.87 billion euros, up 5.4% on an underlying basis from the same period a year earlier. The growth was driven by international operations at its pay-TV unit Canal Plus.

Core operating profits over the period were up by 28% on an underlying basis from a year earlier to 412 million euros, it said, thanks to its advertising unit Havas and Canal Plus. (Reporting by Mathieu Rosemain; editing by David Evans and Paul Simao)