The Transportation Security Administration continues to demonstrate weaknesses in protecting airports against threats, a federal official said Tuesday.

John Roth, the Department of Homeland Security’s inspector general, testified before the Senate Committee on Homeland Security and Governmental Affairs that the agency exposed passengers to "unacceptable risks."

Roth said while government audits over the past year forced the TSA to begin "critically assessing deficiencies in an honest and objective light," the agency continues to use broad risk evaluation guidelines that his office recommended terminating.

Last year, the inspector general released a report disclosing the results of a covert investigation where DHS staff brought mock explosives and weapons through airport checkpoints. TSA screeners failed to discover the weapons in more than 95 percent of cases at dozens of U.S. airports.

The report caused an agency-wide shakeup last June, leading to the reassignment of the acting TSA administrator. Roth added Tuesday that the probe forced the agency to significantly alter its screening process and contributed to more than two dozen corrective actions.

The TSA has since curtailed expedited screening through faster lanes that allowed passengers to keep their shoes on and laptops in cases. The reduction of PreCheck screenings along with agency miscalculations that resulted in low staffing levels caused long security lines this spring.

"Over the past 11 months, we have undertaken a systematic and deliberate transformation of TSA," testified Peter Neffenger, the TSA acting administrator.

Neffenger said that the agency is now vetting employees every day to mitigate insider threats and has retrained staff.

The TSA is set to hire over 700 trained officers in order to cut back on wait times. While this may streamline the security screening process, Roth said there is no substitute to security checkpoints with individual screenings.

"The nature of terrorism today means that each and every passenger must be screened in some way," he testified. "The stakes are enormous. TSA cannot afford to miss a single genuine threat without catastrophic consequences, and yet the terrorist only needs to get it right once."

The DHS will deploy another round of covert security tests this summer to determine the impact of the agency’s changes.