WASHINGTON (AP) – A federal judge approved an immunity deal Friday allowing former Justice Department aide Monica Goodling to testify before Congress about the firing of eight federal prosecutors.

Ms. Goodling, who served as the department’s White House liaison, has refused to discuss the firings without a guarantee that she will not be prosecuted. Congress agreed to the deal, Justice Department investigators reluctantly agreed not to oppose it and Federal District Judge Thomas Hogan gave it final approval Friday.

“Monica Goodling may not refuse to testify,” Judge Hogan began his brief order, which said that Ms. Goodling could not be prosecuted for anything other than perjury in connection with her testimony.

Lawmakers want to question Ms. Goodling as part of an inquiry into whether the Justice Department played politics with the hiring and firing of department officials. What began as an inquiry into whether federal prosecutors were fired for political reasons has grown to include the role of the White House in the firings and whether the Justice Department officials misled Congress about them.

Ms. Goodling’s lawyer has said that, with an immunity deal, she would cooperate and testify honestly.

Justice spokesman Dean Boyd confirmed earlier this month that the department’s inspector general and Office of Professional Responsibility were investigating Ms. Goodling’s role in hiring career attorneys – an unusual responsibility for her to have had.

Investigators are trying to determine whether Ms. Goodling “may have taken prohibited considerations into account during such review,” Mr. Boyd told the AP. “Whether or not the allegation is true is currently the subject of the OIG/OPR investigation.”

Three government officials with knowledge of the investigation said Goodling appears to have sought information about party affiliation while vetting applicants for prosecutors’ jobs. The officials spoke on condition of anonymity because of the ongoing investigation.