The House Ethics Committee said Wednesday that it was investigating allegations that Representative Katie Hill of California, a first-term Democrat considered a rising star in the party, had a sexual relationship with a member of her congressional staff in violation of House rules.
Ms. Hill, 32, has denied the allegation. Her office did not immediately respond to a request for comment on Wednesday night.
The allegation stemmed from a recent report published on a conservative news site, RedState. The report alleged that Ms. Hill had been intimately involved with her legislative director and was separately in a three-way sexual relationship with her husband, whom she is divorcing, and a young campaign aide.
A nude photograph of Ms. Hill and another woman was published and circulated online by conservative critics, some of whom called for Ms. Hill’s resignation. The image was published without Ms. Hill’s consent, and she said she had referred the matter to law enforcement authorities.
Supporters of Ms. Hill said she was a victim of “revenge porn” — illegal under California law.
Members of Congress are barred by House rules from engaging in sexual relationships with their aides, but the rules do not cover campaign staff members.
The Ethics Committee said in a statement on Wednesday that “the mere fact that it was investigating the allegations, and publicly disclosing its review, does not itself indicate that any violation has occurred, or reflect any judgment on behalf of the Committee.”
Ms. Hill, the first openly bisexual congresswoman from California, unseated a Republican, Steve Knight, when Democrats swept to power in the House in 2018. Speaker Nancy Pelosi named her vice chairwoman of the House Oversight and Reform Committee, an unusually high-ranking position for a freshman on a panel that is playing a crucial role in the impeachment inquiry into President Trump.