Three women filed complaints of sexual harassment against the chief executive at the Humane Society of the United States, according to a report citing an internal memo.

The women alleged that Wayne Pacelle made unwanted sexual advances and told one woman that dating him would be beneficial to her career — and threatened to fire her when she refused his request to masturbate in front of her during a work trip in 2006, according to the Washington Post.

An investigation by the law firm Morgan Lewis, which began in December, was first reported last week by the Chronicle of Philanthropy. Pacelle, who earned about $380,000 in 2016, according to the charity’s latest IRS filing, denied the allegations during an interview with the Washington Post.

“This is a coordinated attempt to attack me and the organization,” Pacelle said. “And I absolutely deny any suggestion that I did anything untoward.”

Anna West, a spokeswoman for the nonprofit animal protection organization, declined comment when reached by The Post on Tuesday, referring to a statement released last week confirming the investigation.

“A special committee of the board is overseeing the investigation and reviewing its findings,” according to the statement by Eric Bernthal, chairman of the organization’s board of directors. “We do not have information that can be shared regarding the investigation, its findings, or board actions at this time. We believe it is important to deal in substance and not rumors, and our process is designed to ensure confidentiality and fair consideration of these issues.”

Pacelle did not return a message seeking comment Tuesday. He told the Washington Post he was aware of the ongoing investigation into the allegations, which date back to 2005, one year after he joined the nonprofit.

“There are allegations only,” Pacelle told the Washington Post. “Beware of rumors and other unsubstantiated claims.”

Pacelle denied all three accusations, including that of a third woman who reported that Pacelle dropped by her office one night after she joined the organization in 2012 and started salsa dancing before asking her to join in.

“The one complaint about the salsa dancing, I simply had a conversation with a person and it turned into that,” he told the newspaper. “The person with the hotel — I’m familiar with that. I worked with the person eight years after that allegation. The person never said a thing to me about any harassment, and I certainly never invited her to a hotel room.”