WASHINGTON—The inspector general of the Capitol Police told lawmakers that a police leader’s decision not to make more powerful weapons available to the force could have hampered its response during the deadly Jan. 6 riot at the Capitol.

“It certainly would have provided the department a better posture to repel these attacks,” Michael Bolton said at a hearing Thursday before the House Administration Committee.

Mr. Bolton appeared before the committee after he released an internal report that found multiple instances in which law enforcement failed to incorporate previous intelligence reporting into later assessments and led the department to be underprepared to handle the riot. The report also detailed failures to use all available equipment.

Five people died, including a Capitol Police officer, after a pro-Trump mob stormed the U.S. Capitol to protest a vote certifying the results of the 2020 presidential election.

Mr. Bolton said the Capitol Police needed to improve its intelligence, training and operational planning capabilities and to shift its organizational mind-set. “In regards to culture change, we see that the department needs to move away from the thought process of a traditional police department and move to the posture of a protective agency,” he said.