Washington (CNN) An internal government watchdog has flagged the lack of transparency in the Trump administration's tariff exemption process, saying it "contributes to the appearance of improper influence in decision-making."

memo published this week by the Department of Commerce's inspector general said it found evidence that an unofficial appeals process exists and that communications with an objector prompted a change in the internal review criteria.

"We believe these issues give the perception that the Section 232 exclusion request review process is neither transparent nor objective," the memo said.

The Department of Commerce has processed more than 80,000 requests from US importers asking for an exemption from the steel and aluminum tariffs imposed last year.

Companies may be granted an exemption if they can prove that they can't get the item they need in the United States. But some importers have complained that the review process is opaque. To date, about 60,000 requests have been approved and 20,000 have been denied.

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