The study, performed by the department's inspector general, covers the years 2001 to 2007 and says a politically appointed former department official sought to hire "real Americans" and Republicans for career posts and prominent case assignments, The Washington Post reported Tuesday.
It said the official, former Deputy Assistant Attorney General Bradley Schlozman, favored employees who shared his political views and derided others as "libs" and "pinkos," the newspaper said.
"The department must be vigilant to ensure that such egregious misconduct does not occur in the future," Inspector General Glenn Fine said in a statement released with the report.
Schlozman denied using politics or ideology as a hiring criteria during a June 2007 appearance before the Senate Judiciary Committee.
The findings "confirmed some of our worst fears about the Bush administration's corruption of the Justice Department," Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., told the Post.