After 46 years as the driving force behind Best Buy Co., Richard Schulze resigned as chairman of the board of directors after an investigation revealed that he failed to alert the board about allegations of an inappropriate relationship involving the company's former CEO, Brian Dunn.

Best Buy said Monday an investigation concluded that Dunn carried out a relationship with a female employee that violated company policy. Schulze confronted Dunn with allegations about the relationship in December, but did not disclose them to the board of directors, a breach of corporate governance, the company said.

"The chairman revealed to the CEO the identity of the female employee and the employee who authored the [complaint]," the company said in a statement. "This action exposed the employees to potential retaliation and exposed the company to potential liability for such retaliation."

The board would not learn of the allegations about Dunn for another three months.