The U.K.’s financial regulator has issued over £1 billion ($1.35 billion) of fines for regulated firms’ basic internal control failures in the past five years. This accounted for more than half of the total fines issued to financial services firms in the period.

A new report by the Chartered Institute of Internal Auditors (Chartered IIA) highlights that these fines could, and should, have been avoided with stronger internal compliance and governance policies in regulated financial firms. In many cases, the researchers said, control weaknesses had been repeatedly flagged by compliance and internal audit teams, but the firms had failed to act.

Ruth Prickett graduated from Cambridge University with a BA hons in History and has specialized in business and finance journalism for the past 20 years. She was editor of Financial Management, the magazine...