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.

Italian lender Banco BPM on Tuesday said the unexpected takeover offer by domestic rival UniCredit does not reflect its profitability and could reduce its legal autonomy. UniCredit offered to snap up Banco BPM for roughly $10.

The smaller Italian lender had previously flagged "serious concerns" about the "employment and social impacts" of a potential merger.