Professor William Black:

The straightforward answer is to not allow the bankers to pick the auditors. There should instead be a panel of qualified auditors that are assigned to them, and we should track the performance of those auditors. It would be like relegation. If someone had a record of screwing up, they get yanked from the panel, assuming what they did was not criminal. If it was criminal, they are driven out of business, but if it was just inept, they get relegated. They do smaller accounts and prove over the five years that they can do it right, and then get back up to the "bigs".