Rep. Katie Hill, D-Calif., admitted Wednesday she had an "inappropriate" relationship with a campaign staffer, but denied a report of an affair with her legislative director, all while vowing to cooperate with the House Ethics Committee in its newly launched investigation.

In a letter to constituents obtained by Fox News, Hill acknowledged that in the final years of what she called an "abusive marriage," she began a relationship with the unnamed campaign staffer.

"I know that even a consensual relationship with a subordinate is inappropriate, but I still allowed it to happen despite my better judgment," Hill wrote. "For that I apologize. I wish nothing but the best for her and hope everyone respects her privacy in this difficult time."

She continued, "I am going through a divorce from an abusive husband who seems determined to try to humiliate me. I am disgusted that my opponents would seek to exploit such a private matter for political gain. This coordinated effort to try to destroy me and the people close to me is despicable and will not succeed. I, like many women who have faced attacks like this before, am stronger than those who want me to be afraid."

Hill repeated her denial that she had an affair with a congressional staffer but stated that she was "fully and proactively cooperating with the Ethics Committee."

The committee confirmed earlier Wednesday it was launching an inquiry into Hill in response to the RedState report. That same report also described her relationship with the campaign staffer as a "throuple" with Hill's estranged husband.

"The committee is aware of public allegations that Representative Katie Hill may have engaged in a sexual relationship with an individual on her congressional staff, in violation of House Rule XXIII, Clause 18(a)," Committee Chairman Ted Deutch, D-Fla., and Ranking Member Kenny Marchant, R-Texas, wrote. They added that the panel had launched "an investigation and will gather additional information regarding the allegations."

The statement did not indicate the committee had empaneled an “investigative subcommittee,” the equivalent of a congressional indictment.

Last week, RedState reported that Hill, who is openly bisexual, had developed a "long-term sexual relationship" with the unnamed staffer from her congressional campaign, who ultimately entered into the "throuple" with Hill's husband, Kenny Heslep -- who later filed for divorce. The three of them, according to RedState's confidential sources, had taken multiple vacations together.

The conservative blog obtained screenshots of several text messages between Hill and the staffer detailing the reported end of their three-person relationship earlier this year as well as intimate pictures including a nude photo of Hill. According to the alleged texts, Hill wanted to focus on her work and suggested that "political risk" was a factor.

REP. KATIE HILL FIGHTS BACK AMID CLAIMS SHE WAS INVOLVED IN ROMANTIC 'THROUPLE' WITH STAFFER

RedState also reported that Hill had an extramarital affair with Graham Kelly, her legislative director and former campaign finance director, for at least a year. Heslep was said to have shared his own screenshot of a text exchange he had with a friend who had heard about the affair, which he later deleted from his Facebook account. According to RedState, the alleged affair was why Heslep filed for divorce.

Fox News is told there is no U.S. Capitol Police investigation into the photos because the revelation of the images could be a violation of state law, not federal law.

"Intimate photos of me and another individual were published by Republican operatives on the Internet without my consent," Hill said in an earlier statement to Fox News. "I have notified Capitol Hill police, who are investigating the situation and potential legal violations of those who posted and distributed the photos, and therefore will have no further comment on the digital materials."

She did add this: "I am disgusted that my opponents would seek to exploit such a private matter for political gain. This coordinated effort to try to destroy me and people close to me is despicable and will not succeed. I, like many women who have faced attacks like this before, am stronger than those who want me to be afraid."

The freshman congresswoman also flatly denied having an affair with Kelly, adding that her estranged husband made the "vindictive claims."

"Allegations that I have been involved in a relationship with Mr. Kelly are absolutely false," Hill told Fox News. "I am saddened that the deeply personal matter of my divorce has been brought into public view and the vindictive claims of my ex have now involved the lives and reputations of unrelated parties."

"She continued: "This smear campaign will not get in the way of the work I am doing every day to move our district and our country forward. I am truly grateful for the outpouring of support I have received from colleagues and constituents alike, and I know we will get through this together."

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Neither Heslep nor Kelly could be reached for comment.

Fox News' Mike Emanuel and Chad Pergram contributed to this report.