This was confirmed by four sources close to the matter.
Yesterday, Mediobanca announced the postponement of today's ordinary shareholders' meeting to September 25.
Piazzetta Cuccia announced its proposal to acquire Banca Generali in April in an attempt to fend off a public exchange offer by Banca Mps, which has the support of the government.
Mps is expected to formally launch its hostile bid in July, one of many deals announced in the Italian banking sector that could lead to a significant reshaping of the industry. The deal was announced in January, but it will take several months to obtain all the necessary approvals.
If the MPS offer goes through, it would cast doubt on Mediobanca's ability to proceed with its takeover of Banca Generali.
Mediobanca CEO Alberto Nagel described the Banca Generali deal as an alternative to the MPS deal, hoping that Piazzetta Cuccia would become too big a bite for Siena.
Shareholders who want to oppose the bid for Banca Generali have accumulated a combined stake of 11% in the last month, according to one of the sources.
This has tipped the likely outcome of today's vote against Nagel and prompted the board to decide to postpone the meeting, according to sources who spoke on condition of anonymity.
The vote was likely to see around 40% of the capital abstain or vote against, according to a fifth source.
JUDICIAL INVESTIGATION
The opposition is led by Francesco Gaetano Caltagirone, who recently increased his stake in Mediobanca to around 10% from 7% and can count on the support of UniCredit CEO Andrea Orcel.
UniCredit, which is facing government opposition to its bid for Banco Bpm, holds a 1.9% stake in Mediobanca as part of its equity trading activities. By abstaining, it would have helped the opposition.
Nagel has long been the target of criticism from Caltagirone and Delfin, the holding company of Leonardo Del Vecchio's heirs led by Francesco Milleri, who became shareholders of MPS during the last sale of a stake by the Treasury.
The placement is under investigation by the Milan Public Prosecutor's Office.
According to sources, by postponing the meeting, Mediobanca has gained time to await developments in the investigation.
While Milleri appreciated Nagel's efforts to change Mediobanca, Caltagirone rejected the Banca Generali deal outright, saying he saw no value in it.
Milleri and Caltagirone are also major shareholders in Generali, the controlling shareholder of Banca Generali.
Mediobanca intends to use its 13% stake in Generali as a counterparty for Banca Generali, cutting its historic ties with Trieste and responding to criticism levelled at Nagel by Delfin and Caltagirone regarding the excessive influence of Piazzetta Cuccia on the Trieste-based company.
The latest battleground was Generali's April shareholders' meeting, which saw the renewal of the board of directors and a landslide victory for Mediobanca's list, despite UniCredit voting with its 6.5% stake for Caltagirone's list.
(editing Stefano Bernabei)
