Former Bank of America Corp. Chief Executive Kenneth D. Lewis and the company's current consumer-banking chief were accused in a civil complaint of duping investors by failing to disclose mounting losses at Merrill Lynch & Co. before shareholders approved the securities firm's takeover by the giant bank.

The New York attorney general's allegations Thursday came as the Securities and Exchange Commission said it reached a $150 million settlement of a federal suit alleging that the Charlotte, N.C., company misled investors about...