DENVER – The University of Denver Sturm College of Law pays its male professors significantly more than its female professors, and the federal government recently vowed to sue the school if it doesn’t fix the discrepancy.

The U.S. Equal Employment Opportunity Commission’s Denver office sent a letter to the university late last week outlining its investigation into a gender pay gap at the law school going back to 1973. A 2012 memo sent out by the school’s dean shows full female professors took home $16,000 less per year on average than males, which the EEOC cites as evidence the school was aware of the issue “but took no action to ameliorate this disparity, in effect intentionally condoning and formalizing a history of wage disparity based on sex,” The Denver Post reports.

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“I never would have suspected the law school was breaking the law like this until I started looking into it,” said longtime DU law professor Lucy Marsh, who filed the initial complaint two years ago that launched the EEOC investigation.

“I think it’s wonderful,” she said. “I am delighted that the EEOC has seen this as a big, systemic problem, and they are going after the big problem.”

According to the 2012 memo, Marsh, who has worked for DU for 40 years, made roughly $109,000 a year as the law school’s lowest paid full professor. The school’s median salary for professors was $149,000 that year, the Post reports.

The EEOC wrote in its letter that the law school must give female professor wage increases and back pay to comply with the Equal Pay Act, and threatened to sue the school on behalf of its female professors if it doesn’t act, according to 9 News.

Marsh told the Post the back pay could cost the school up to $1.2 million, and any settlement would force officials to pay male and female instructors the same for similar positions.

Law school officials declined to discuss the EEOC letter on camera with 9 News, but instead provided a defiant statement.

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“In this era of cost containment and assessment we stand by our historical system of evaluation and merit pay,” DU chancellor Rebecca Chopp said.

“DU said an independent consultant found no correlation between pay and gender at the law school. The university also claims Professor Marsh’s pay lags behind others because of her ‘sub-standard performance in scholarship, teaching and service,’” 9 News reports.

The university contends it hired a private consultant to review its pay practices and the consultant found no evidence gender plays a role in determining compensation. The lower pay for women professors stems instead from how the school evaluates professors’ rank, duties, age and performance.

Melissa Hart, a University of Colorado employment law professor, told the Post the Equal Pay Act doesn’t consider whether institutions intend to discriminate against women, but rather tasks employers to fix pay discrepancies if and when they come to light.

“That’s what the Equal Pay Act says,” Hart said. “If you see it, you have to fix it.”