HARRISBURG — State Rep. Brian Ellis resigned his seat on Monday — six days after a woman accusing him of sexual assault filed a formal complaint with the majority state House Republicans.

“It is with immense gratitude to the sacrifices made by my family, the support of my constituents, and the friendship of my colleagues that I have concluded that it is in the best interests of my family, the residents of the 11th House district, and my own health that I resign from the General Assembly,” Ellis, a Republican from Butler County in Western Pennsylvania, wrote in a two-paragraph resignation letter submitted to the House Speaker.

An attorney for Ellis did not immediately comment. In a statement issued last week, the law firm representing him, Myers, Brier & Kelly LLP, described the accusations as “just plain false” and an effort to “generate sensational press coverage.”

Ellis’ resignation is effective immediately. He has been listed on medical leave each session day this year, according to a spokesman for House Republicans. It is unclear why he was on medical leave.

Jennifer Storm, the state’s victim advocate, who has acted as a spokesperson for the woman, called Ellis’ decision to resign a sign that there is “a new day in Harrisburg.”

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“We finally saw a survivor come forward, and she was believed, and treated with dignity and respect by the House — and we are seeing a real life consequence to that,” said Storm. “In cases involving allegations against public officials, unfortunately, the M.O. has just been to kind of ride it out. That didn’t happen here.”

House Republican leaders hadcalled on Ellis to resign in January, after news broke that the Dauphin County district attorneywas investigating allegations that he had sex with a woman in late 2015 while she was incapacitated and without her consent. That investigation continues.

Last week, the woman filed a formal complaint with an attorney representing the GOP caucus and its members on the Ethics Committee, which has the power to recommend various sanctions, up to removing someone from the House.

The woman wrote in her complaint that she went to a Harrisburg bar with a friend in October 2015, believes she had less than two drinks and then “was in a state of blackout.” She wrote that she woke up in Ellis’ bed the next morning, naked and in pain. When she confronted Ellis, he told her they had sex, and she believes was raped, according to her complaint.

The Inquirer and the Pittsburgh Post-Gazette do not identify victims of alleged sexual assaults unless they wish to be named. The woman works in state government but not directly for Ellis.