Concerns are mounting over Bank of America's ability to hold on to its most senior advisers across its divisions, including top relationship banker Andrea Orcel, as the bank’s wealth business was hit by the withdrawal of billions of dollars by Merrill Lynch clients.

Two of the most senior departures from Bank of America to date include Merrill Lynch president Gregory Fleming and Robert McCann, vice chairman of the company's global wealth management division, both of whom resigned on January 1.