One of former state Attorney General Eric Schneiderman's sex accusers has written a memoir about their nightmare relationship — claiming he even threatened to kill her if she ever left him.

Publicly, Schneiderman championed women’s rights, Tanya Selvaratnam says in touting her new memoir, "Assume Nothing: A Story of Intimate Violence."

But privately, he horribly abused her, says Selvaratnum — who the ex-AG allegedly called his "brown slave" — in a video promotion for the book shared with The Post.

"He was the Attorney General of New York State, and was getting national recognition as a progressive hero and a key ally of the 'Me Too' movement," Selvaratnum wrote, referring to when their relationship started in 2017.

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"I was scared to come forward because he had told me he could have me followed. He could have my phone tapped.

FILE - New York Attorney General Eric Schneiderman resigned following allegations of sexual misconduct.

FILE - New York Attorney General Eric Schneiderman resigned following allegations of sexual misconduct. (Reuters)

"On some occasions, he said if we broke up he would have to kill me.

"But when I found out that I was not the first woman he had abused, and realized that I would not be the last, I knew that I had to come forward," Selvaratnum wrote in her tome, which is published by HarperCollins and comes out Tuesday.

Selvaratnam is one of four women to allege sexual harassment and physical abuse by Schneiderman, who abruptly resigned as state Attorney General in May 2018, just hours after the women’s bombshells dropped in The New Yorker.

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Selvaratnam describes her experiences as Schneiderman’s girlfriend in the book, saying that at first, she was smitten by his committment to feminism and social justice — and to his fight against then-president’s Donald Trump's "attacks on civil liberties and vulnerable communities."

He spoke to her of hoping to run for governor, implying that she would be his first lady, she said.

Soon, though, the fairy tale romance turned dark, she wrote.

Sevalratnum realized her powerful beau’s pals included Harvey Weinstein and that he was, in her words, an alcoholic who abused sleeping pills and anti-anxiety meds.

She’d find the then-AG "staggering around the apartment" on some nights, she wrote. In January of 2017, Schneiderman got so drunk he fell in his bathroom and needed facial stitches — and told her to say he had fallen while jogging, she said.

In bed, he was violent, physically and verbally, the accuser has recounted. He would allegedly choke her, spit at her and slap her until she called him "Master" or "Daddy."

The first slap in the face during sex happened just six weeks into the relationship, she wrote.

"Over time, the slaps got harder and began to be accompanied by demands," Sevalratnum wrote.

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"In bed, he would slap me until I agreed to find him a young girl for a three-way," she said.

She repeatedly pretended to him that she would, she wrote.

The Sri-Lanka-born Selvaratnam well remembers her own mother’s abuse at the eye-blackening hands of her father.

She herself stayed with Schneiderman for nearly a year, feeling trapped and intimidated like many domestic violence victims, she said.

He could be "charming and charismatic," she conceded, and "often supportive,"

But she was terrified that "he and his people [would] try to crush me" if she went public, and left the relationship only with the help of a domestic violence expert, she wrote.

"Writing ‘Assume Nothing’ was painful and emotional, but it was also liberating," she said.

The book ends with a lengthy appendix listing organizations that aim to help women who are victims of intimate partner violence find the courage and resources to leave.

"I wrote my way out of the darkness," Sevaratnum wrote. "A victim looks like all of us. Even fierce women get abused."

The book is being hailed as "courageous and compelling" by Kirkus Reviews, and as a "searing, yet sensitive account of vulnerability and redemption that will find a wide audience," by Library Journal.

Schneiderman, 66, was last heard of in January of 2019, when he completed his training at a Manhattan based school that certified him as a meditation teacher.

He has been pursuing therapy and meditation practice "as part of his recovery program," a rep told The Post at the time. He could not be immediately reached for comment.

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But in 2018, he told the New Yorker in a statement, "In the privacy of intimate relationships, I have engaged in role-playing and other consensual sexual activity. I have not assaulted anyone. I have never engaged in nonconsensual sex, which is a line I would not cross."

Selvaratnam's film producing credits include the 2014, Emmy-nominated "Born to Fly;" her previous books include "The Big Lie: Motherhood, Feminism and the Reality of the Biological Clock."