Mayor Eric Adams asked a colleague for oral sex in exchange for career help in 1993 and sexually assaulted her when she refused, she said in a legal complaint filed on Monday.

The detailed complaint, which is part of a lawsuit that was originally filed in November in Manhattan under the Adult Survivors Act, said that the woman, who worked with Mr. Adams at New York City’s transit police bureau, asked him for help after she had been passed over for a promotion.

Mr. Adams, who was a police officer, drove the woman, an administrative aide with the department, to a vacant lot and requested oral sex, according to the 26-page complaint. When she declined, he forced her to touch his penis and ejaculated on her leg, the complaint says.

“The effects of that sexual assault, betrayal and astonishing abuse of power, continue to haunt plaintiff to this day,” the complaint said.

Mr. Adams, a Democrat, has repeatedly denied assaulting the woman. The mayor’s office did not immediately respond to a request for comment on Monday.

Addressing the allegations at a community meeting in December, he dismissed them, saying: “That is not who I am.”

“I want to be very clear: Never happened,” he said. “I don’t even know who the person is. I don’t even remember if I ever met them before.”

New York’s Adult Survivors Act, which was signed into law by Gov. Kathy Hochul in 2022, provided a one-year window for people to bring lawsuits over sexual assaults that may have occurred years or decades ago.

The woman filed a brief notice of claim in New York Supreme Court in November, just before the law’s one-year grace period expired, accusing Mr. Adams of assaulting her.

But the new complaint goes into greater detail and accuses Mr. Adams of requesting a “quid pro quo sexual favor.” It says that the woman was particularly fearful during the alleged assault because she believed that Mr. Adams, as a police officer, had a loaded gun in the car.

The woman, who now lives in Florida, joined the transit police bureau as an administrative aide in 1980 and stopped working for the city in 1994, according to the complaint.

Her lawyer, Megan Goddard, said in a statement that she was proud of her client.

“She knew that filing this lawsuit would cause her significant personal challenges, but she did so nevertheless, because she believes sexual abusers must be held to account, no matter who they are,” she said.

The lawsuit against Mr. Adams seeks $5 million and also names the Police Department and the Guardians Association, a fraternal organization of Black police officers, as defendants. Mr. Adams was active in the Guardians at the time of the alleged assault.

In addition to sexual assault, the woman accuses Mr. Adams and the department of gender discrimination, retaliation, creating a hostile work environment and inflicting emotional distress.

The plaintiff has filed other lawsuits in the past. In 2008, she sued American Airlines and lost, arguing that an employee had caused her to fall out of a wheelchair, injuring her back.

She sued the Miami-Dade County Public Schools Board in 2009, arguing that she was denied compensation after she was attacked by a student. She lost at trial and then appealed parts of the decision to the Florida Supreme Court and the United States Supreme Court, where she won several procedural motions but failed to win a retrial.

Mr. Adams was an officer in the transit police bureau at the time of the alleged assault in 1993. He joined the Police Department in 1995, after the transit bureau was absorbed into the larger agency.

After more than two decades as a police officer, Mr. Adams served as a state senator and Brooklyn borough president before he was elected mayor in November 2021.

The complaint said that the plaintiff sought help from Mr. Adams because he had been an advocate for Black employees within the Police Department. She said she repeatedly said “no” to him during the alleged assault and that she was “sickened and outraged” by his behavior.

She said she did not come forward with the allegations at the time because she was a divorced mother of young children and feared she could lose her job.