CHICAGO — In a pointed rebuke to the Environmental Protection Agency, an internal watchdog concluded on Thursday that the agency should have acted more swiftly to warn residents of Flint, Mich., that their water was contaminated with lead.

The report, issued by Arthur A. Elkins Jr., the inspector general for the E.P.A., blamed the federal government for inaction in Flint, echoing the sentiments of many Republicans who have said for more than a year that the agency failed in its oversight role.

Gov. Rick Snyder of Michigan, a Republican, has said that while he accepts his share of blame for the contamination of Flint’s water, he also believes officials on the local and federal levels were partly responsible.

In an 11-page report, Mr. Elkins said that E.P.A. officials had enough information and authority to issue an emergency order under the Safe Drinking Water Act as early as June 2015. At that time, officials knew that “systems designed to protect Flint drinking water from lead contamination were not in place, residents had reported multiple abnormalities in the water, and test results from some homes showed lead levels above the federal action level.”