BATON ROUGE, La. (AP) — A Senate committee chairman is pressing Justice Department officials for more information about their response to "whistleblowing" claims by a suspended FBI agent who investigated a former Louisiana district attorney accused of trading sex for leniency.

Senate Judiciary Committee Chairman Charles Grassley, an Iowa Republican, says FBI Special Agent Mike Zummer told the committee that a relationship between a federal prosecutor and a defense attorney may have led to a lenient plea agreement for former St. Charles Parish District Attorney Harry Morel.

In 2013, Zummer filed an ethics complaint against New Orleans-based federal prosecutor Fred Harper, who once co-owned a condominium with Morel's attorney, Ralph Capitelli.

The FBI suspended Zummer without pay earlier this year — and suspended his security clearance — after he outlined his conflict-of-interest allegations in a letter to the judge who sentenced Morel to three years in prison.

"That looks like it could be a misuse of the security clearance process to mask retaliation for protected whistleblowing," Grassley wrote in Nov. 15 letters to Attorney General Loretta Lynch and FBI Director James Comey.

A spokesman for Grassley's committee said in an email Thursday that it hasn't received any responses to the letters.

U.S. District Judge Kurt Engelhardt sentenced Morel in August after he pleaded guilty to obstructing the FBI investigation. Zummer's 31-page letter to the judge remains under seal, but Engelhardt said it raised legitimate concerns that the Justice Department is either "unable or unwilling" to self-police ethical lapses within its ranks.

At a news conference following Morel's guilty plea, state and federal authorities accused Morel of being a sexual predator who solicited sex from at least 20 women in exchange for favorable treatment from his office. But they haven't charged Morel with any sex crimes. His attorney accused prosecutors of engaging in a smear campaign to influence sentencing.

Federal prosecutors initially declined to prosecute Morel. Grassley's letter says Harper was "reportedly directly involved in that decision." But the case was revived by U.S. Attorney Kenneth Polite after he took office in 2013.

Grassley's letter to Comey asks if the FBI ever had concerns about the relationship between Harper and Capitelli.

Harper, who declined to comment Thursday, said in September that the complaint Zummer filed with the Justice Department's Office of Inspector General "was reviewed by the appropriate authorities and found to be unsubstantiated."

Capitelli said in a statement that Zummer is a "disgraced rogue FBI agent who is trying to desperately salvage his career." Capitelli also said it was his "understanding" that Harper recused himself from "any decision making" in Morel's case.

"These same totally unsupported allegations haven't gotten any better with age," the defense attorney added. "They are still totally inaccurate and untrue."

Morel, 73, is serving his sentence at a low-security prison in Seagoville, Texas.