Former Wells Fargo CEO John Stumpf told Congress under oath last month that he wasn't notified of a serious fake account problem at the bank until 2013.

However, CNNMoney has obtained a 2007 letter addressed to Stumpf that warned of widespread "unethical (and illegal) activity" inside Wells Fargo and the "routine deception and fraudulent exploitation of our clients."

The letter was written by a Wells Fargo (WFC) employee, who had been transferred from the branch after raising sales concerns, and who later won a federal whistleblower retaliation case against the company. Read More