The board is elected for a three-year term, and the current one expires on Oct. 28, when Mediobanca shareholders will vote on its renewal, including the chief executive.

Mediobanca's outgoing board has proposed 15 members, including a new term for current CEO Alberto Nagel and Chairman Renato Pagliaro.

Two other slates were submitted by Delfin, the holding company of the late Italian billionaire Leonardo Del Vecchio and the main investor in the bank with a 19.7% stake, and by a group of fund managers with an overall 2% stake.

While Delfin's slate does not pose a direct challenge to either Nagel or Pagliaro, its decision to put forward its own nominees increases uncertainty in the short term and could lead to a fractured board, analysts have said.

Del Vecchio, who died last year at the age of 87, had criticised Nagel for failing to grow the investment bank's business decisively and holding back expansion at insurer Generali, in which Mediobanca is the main shareholder.

On Wednesday, proxy adviser Institutional Shareholder Services (ISS) said it was recommending that Mediobanca investors vote in favour of the outgoing board's slate of nominees.

(Reporting by Gianluca Semeraro; editing by Gavin Jones and Kirsten Donovan)