Former child star Mackenzie Phillips, the daughter of Mamas and Papas leader John Phillips, alleges in a new tell-all book that she had a long-term sexual relationship with her father, and that he introduced her to intravenous cocaine use, People reports.

In the book, titled High on Arrival, the younger Phillips confesses that the relationship began the night before her 1979 wedding to Jeff Sessler, a member of the Rolling Stones’ entourage. John had become pals — and notorious drug buddies — with the Stones after moving to London in 1973.

“On the eve of my wedding, my father showed up, determined to stop it,” writes Phillips, who was 19 at the time. “I had tons of pills, and Dad had tons of everything too. Eventually I passed out on Dad’s bed.”

“My father was not a man with boundaries. He was full of love, and he was sick with drugs. I woke up that night from a blackout to find myself having sex with my own father.”

“Had this happened before? I didn’t know. All I can say is it was the first time I was aware of it.”

Mackenzie, who appears on Oprah this afternoon, told the talk show host that her father introduced her IV cocaine use, CBS reports. “He put the needle in my arm and pushed the plunger in and he missed.”

“Missed the vein?” Winfrey asked.

“Missed the vein,” Mackenzie replied, “and my whole arm went numb, because it was cocaine.”

In 1982, Mackenzie’s drug use had reached a breaking point. She was fired from TV series One Day at a Time and entered a rehab facility with her father, where their relationship continued, she writes.

Soon the relationship became consensual, with Mackenzie even joining a reformed version of the Mamas and the Papas. Her dad even suggested that they move to a country where incest was accepted, the LATimes reports.

“One night Dad said, ‘We could just run away to a country where no one would look down on us. There are countries where this is an accepted practice. Maybe Fiji.’”

Mackenzie’s half-sister, Chynna Phillips of the 1990s group Wilson Phillips, tells UsWeekly that Mackenzie dropped the bombshell news during a phone call in 1997.

“She said, ‘I don’t know why, but I just really felt the need to call you and tell you something that I think you need to know,’” Chynna said. “And she went on to tell me that she had had an incestuous relationship with our dad for about 10 years.”

Mackenzie, now 49, was arrested for heroin and cocaine possession at the Los Angeles airport in 2008. John Phillips, who had a liver transplant in the 1990s and was seen drinking alcohol soon after (“I was just trying to break in the new liver,” he said), died in 2001 from heart failure. On his deathbed, Mackenzie forgave him, she writes.

“I would not be the woman I am, had I not been your daughter,” she says she told him. “So, I want you to know that I forgive you, and I love you very, very much.”