Bank of America chief executive officer Ken Lewis will soon inform or has already informed his board of directors that he will be stepping down by the end of the year, according to CNBC.

Lewis reached the decision entirely on his own in recent days, reported CNBC's Charles Gasparino, citing impeccable sources.

Bank of America confirmed after the report that Lewis will be retiring by the end of the year, according to CNBC. 

Lewis and the bank are being investigated by Congress, regulators and the state of New York for their role in the company's acquisition of Merrill Lynch in 2008, focusing on when and how executives knew about undisclosed losses at Merrill Lynch and the size of bonuses to Merrill employees.

Update 5:34 p.m.

Ken Lewis quote from Bank of America press release on retirement:

Bank of America is well positioned to meet the continuing challenges of the economy and markets, said Lewis. I am particularly heartened by the results that are emerging from the decisions and initiatives of the difficult past year-and-a-half.

The Merrill Lynch and Countrywide integrations are on track and returning value already, Lewis noted. Our board of directors and our senior management include more talent, and more diversity of talent, than at any time in this company's history. We are in position to begin to repay the federal government's TARP investments. For these reasons, I decided now is the time to begin to transition to the next generation of leadership at Bank of America.