The scope and length of time of the unsolicited account mess at Wells Fargo needs to be investigated, Sen. Bob Corker told CNBC on Tuesday, ahead of the morning hearing before his Senate Banking Committee panel.

The Tennessee Republican said there are "legitimate concerns" over the practices that led to the bank's $185 million settlement with regulators earlier this month over charges employees boosted their sales targets and bonuses by opening accounts for unsuspecting customers.