The brokerage industry’s self-regulator has asked employees fired by Wells Fargo & Co. WFC, -2.38%   and stripped of their securities registrations to come forward if they have concerns over their treatment, the latest sign of growing scrutiny on the bank.

The request from the Financial Industry Regulatory Authority, or Finra, comes as lawmakers question whether Wells Fargo wrongfully fired employees who pushed back on questionable sales practices and sometimes mischaracterized their behavior on their industry records.

In response to an inquiry by Sens. Elizabeth Warren (D., Mass.), Ron Wyden (D., Ore.), and Bob Menendez (D., N.J.), Finra has said that more than 600 Wells Fargo employees fired during the five-year period that encompassed the bank’s cross-selling scandal had received termination filings known as Form U5s. Such forms document the reasons for the dismissal of brokerage employees, and negative justifications can hinder an adviser from gaining employment elsewhere in the…