State Attorney General Eric Schneiderman called his Sri Lankan girlfriend his “brown slave” and wanted her to refer to him as “Master,” the woman says.

Harvard-educated activist writer Tanya Selvaratnam told the New Yorker magazine that her yearlong affair with Schneiderman “was a fairytale that became a nightmare” — and quickly escalated into violence in the bedroom, even as he begged for threesomes.

“Sometimes, he’d tell me to call him Master, and he’d slap me until I did,” Selvaratnam said.

“He started calling me his ‘brown slave’ and demanding that I repeat that I was ‘his property.’”

Selvaratnam said, “The slaps started after we’d gotten to know each other.

“It was at first as if he were testing me. Then it got stronger and harder. It wasn’t consensual. This wasn’t sexual playacting. This was abusive, demeaning, threatening behavior.”

She said that as the violence grew, so did his sexual demands.

“He was obsessed with having a threesome and said it was my job to find a woman,” Selvaratnam said. “He said he’d have nothing to look forward to if I didn’t and would hit me until I agreed.”

She said she had no intention of adding a second woman to their bed.

The abuse increased until Schneiderman was not only slapping her but spitting on her and choking her, she said.

“He was cutting off my ability to breathe,” she said.

Soon, “we could rarely have sex without him beating me.”

The attorney general was often fueled by booze, Selvaratnam said.

And he would push her to drink, too, she said.

“Drink your bourbon, Turnip,’’ she said he ordered her, using his nickname for her.

A friend finally helped her leave him, Selvaratnam said.

Schneiderman told the mag 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.”