The national legal director of the American Civil Liberties Union (ACLU) David Cole will testify against Republican Alabama Sen. Jeff Sessions at his confirmation hearing to be the next U.S. attorney general.

“The ACLU is nonpartisan, and as a matter of longstanding policy does not support or oppose nominees for federal office. As a result, the ACLU rarely testifies in confirmation hearings,” a Saturday statement from the ACLU said. “However, the organization is taking the extraordinary step of testifying in this hearing because Sen. Sessions’ record raises significant, serious questions about his hostility to civil rights and civil liberties.”

The civil rights group did not specifically say they will oppose Sessions’ nomination, only that “The ACLU believes he must satisfactorily answer questions on these issues before a confirmation vote proceeds.”

The ACLU and Sen. Sessions have a long and tense relationship. The Alabama senator has in the past allegedly called the organization “communist” and “un-American.” The ACLU has criticized his stances on gay marriage, capital punishment and other issues for years.

The ACLU is not the only left-leaning civil rights group that has come out against Sessions’ AG nomination. The NAACP has been very vocal in its opposition of the senator becoming the next attorney general and even launched a sit-in at his Mobile, Alabama office to protest his confirmation. (RELATED: NAACP Occupies Sessions Office Demanding Withdrawal From AG Nomination)

Sessions’ confirmation hearing is scheduled to start Tuesday.