The whistle-blower helping the U.S. government mount a $1 billion fraud lawsuit against Bank of America Corp. was himself accused of fraud by an investor in a financing company he co-founded, and now works at Fannie Mae, one of two entities he claims the bank defrauded, Bloomberg News reported on Friday. Edward O’Donnell sued Bank of America, the second-biggest U.S. lender by assets, in February under the False Claims Act, saying that the bank's Countrywide Financial unit, where he once worked, issued defective mortgages and sold them to Fannie Mae and Freddie Mac. Last month, the Justice Department joined his suit, making it the first time the U.S. has accused a bank of fraud over loans sold to the two government-sponsored mortgage- finance companies.