Madigan has been linked in court documents to a bribery scheme involving the company, but has not been charged.
In a letter obtained by the Chicago Tribune Friday night, Madigan says, "For the record, I am not exercising my fifth amendment rights by not appearing before the committee. As I have said before, I have done nothing wrong."
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He goes on to state, "the federal investigation is more important than Mr. Durkin's political theatrics, and I cannot in good conscience take any action that may, in any way, interfere with a federal investigation."
However, Madigan was formally accused of "conduct unbecoming of a legislator" earlier this month, which is not a criminal charge.
Republicans filed the formal charge Sep. 10 accusing Madigan of breaching the public trust and conduct unbecoming of a legislator as detailed in the federal case against ComEd.
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"Including engaging in a bribery scheme, an extortion scheme conspiracy to violate federal and state laws, amongst other misconduct and misuse of the office," House Republican Leader Jim Durkin said at the time of the charge.
Madigan has previously called the investigation a political stunt.