CHAPEL HILL, North Carolina — An advocacy group wants the University of North Carolina system president to address the treatment of a former UNC-Chapel Hill learning specialist who questioned the literacy levels of some school athletes.

In a letter to Thomas W. Ross on May 6, Government Accountability Project president Louis Clark wrote of concerns over “continued mistreatment, harassment and retaliation” against Mary Willingham, who left her job earlier this month.

She had told CNN in January that the majority of football and basketball players she looked at from 2004-12 read at below-grade levels.

The Washington, D.C.-based nonprofit, which calls itself the nation’s leading whistleblower protection and advocacy organization, released a copy of the letter Wednesday.

Clark wrote to Chancellor Carol Folt in March, saying UNC might have violated state law in criticizing Willingham’s research. He sought an investigation into whether school officials have harassed or intimidated her.

In April, three outside researchers said their review found Willingham’s data did not support low athlete literacy claims. Willingham said researchers did not have all information she used for her findings, and Clark’s latest letter questioned that review.

He asked Ross — who oversees the 17-campus state university system — to investigate Willingham’s treatment and “invite” her to stay in her former job.

It also asks whether an investigation of academic fraud by former U.S. Justice Department official Kenneth Wainstein includes questions of Willingham’s treatment. The fraud included no-show classes in the African studies department requiring a paper at semester’s end, which Willingham said were used to keep many athletes eligible.