Federal officials may have lost millions of dollars in revenue because they didn't properly review fees charged by the Environmental Protection Agency, according to a government watchdog.

"We believe that the EPA could help the federal government reduce the budget deficit by performing more thorough biennial user-fee reviews that identify potential additional revenue," the EPA inspector general said in a recent report.

Officials may also have failed to charge fees that should have been assessed because they didn't review all of EPA's programs, the IG said.

The EPA's failure to assess one such program lost the agency as much as $8.9 million in annual revenue, the IG said.

Federal law requires the EPA to do cost reviews on programs that provide services, goods or resources to insure the agency charges appropriate fees for things like rent, royalties and licenses.

The IG said EPA officials also failed to provide complete reports to the Office of Management and Budget.

In its 2008-09 and 2010-11 reviews, the agency gave OMB total fee revenues but not the costs of the programs involved.

Since then, the EPA has issued a new review guide, conducted training personnel on the biennial reviews and increased review oversight, the report found.