Italy's Banco BPM, the target of an unsolicited all-share offer announced by UniCredit, should remain an independent bank, its CEO said in a letter to staff on Wednesday, warning of big job cuts if the deal went through.

The Italian lender rejected the offer from its larger rival, saying it undervalues the bank and creates uncertainty.

Italy's Banco BPM on Tuesday rebuffed a 10 billion euro ($10.5 billion) unsolicited takeover offer by rival UniCredit, saying it undervalued the bank, tied its hands in strategic deals and created new risks for shareholders.