A Pennsylvania state representative resigned on Monday, days after a woman made a complaint to the state's Republican caucus alleging that he sexually assaulted her in 2015 when she was blacked out.

"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 interest of my family, the residents of the 11th House district, and my own health that I resign from the General Assembly," State Rep. Brian Ellis wrote in his resignation letter submitted on Monday.

Ellis' resignation came after House Republicans in January called on him to step down when the Dauphin County district attorney began to investigate allegations that Ellis had sex with a woman without her consent in October 2015, according to the Philadelphia Inquirer.

"It truly has been a new day for survivors," the woman's lawyer, Christine Wechsler told NBC News on Tuesday. "This is an acknowledgment of the credibility of the allegation."

She added that her client feels "vindicated" after hearing of Ellis' resignation from public office.

The woman said that she had been out "casually drinking" in a Harrisburg bar when she began to have "scant memories." The next thing she remembers is waking up "in pain, injured and naked" in bed with Ellis, according to a formal complaint she addressed to an attorney representing the state's GOP caucus and its members on the Ethics Committee on March 12.

The five-page complaint was obtained by numerous local outlets and published online.

The law firm representing Ellis, Myers, Brier & Kelly LLP, described the accusations as "just plain false," in a statement to NBC News.

"This anonymous complaint was prepared by the accuser's hired agents—and then instantly given to numerous media outlets—for one cynical reason: to generate sensational press coverage," the law firm said.

In the complaint, the woman said she believed she was raped but that when she woke up and confronted Ellis, 49, a married Republican from Butler County, he told her they had sex.

Up to that night, she describes that her experiences with Ellis consisted of "socializing" on less than a dozen professional and networking occasions, according to the complaint.

However, she said that during those interactions, Ellis "repeatedly injected sexual innuendo into the conversation" and that he "explicitly" made his sexual interest in her known. She said that each time this occurred, she made it "abundantly clear" that his feelings were not reciprocated.

Wechsler said that the woman is cooperating with law enforcement agents on their investigation into her allegations. A call to the Dauphin County district attorney's office was not returned.

The woman said the reason she did not immediately report the incident was because of fear of professional and personal retaliation. Her attorney said that she works for the Pennsylvania state government but not directly for Ellis.

"I felt powerless," she said in her complaint. The woman said the reason she came forward now is that the state's House of Representatives recently created a process to work through sexual assault complaints.

"I realize I am strong enough to help ensure that the House of Representatives rids itself of a member who is not deserving of the public's trust," she said.