Democrat Harry Benton serves the 97th District, covering parts of Plainfield and other southwest suburban communities.
Speaker Welch released a statement Wednesday saying his office received reports concerning Benton's conduct, but did not specify the allegations.
Speaker Welch notified the House Chief Ethics Officer. The Legislative Inspector General investigated.
Speaker Welch said the findings, "reveal clear patterns of conduct by Representative Benton that are outrageous, unethical, and unbecoming of a member of the Illinois House of Representatives."
Speaker Welch said if Benton does not resign, he will start the process of expelling him from the house.
ABC7 has reached out to Representative Benton for comment but have not heard back yet.