MACKENZIE PHILLIPS CLAIMS HER FATHER INTRODUCED HER TO HEROIN & HAD SEX WITH HER FOR YEARS!

Former child star Mackenzie Phillips claims in a new explosive tell-all book that she had an incestuous affair with her father, John Phillips, leader of the famed '60s pop group the Mamas and the Papas - a long-term relationship that grew to be consensual.
In "High on Arrival," out Wednesday, Phillips describes emerging from a blackout to find herself engaging in intercourse with her dad - on the night before her wedding, People.com reports.

"On the eve of my wedding, my father showed up, determined to stop it," she writes. "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. For a moment I was in my body, in that horrible truth, and then I slid back into a blackout."

Both father and daughter waged public battles with drug addiction. John Phillips died in 2001.

The younger Phillips' substance abuse problems ultimately led to her firing from "One Day at a Time," the sitcom on which she starred in the early '80s. Afterward, she entered rehab - with her dad, People reports.

As Mackenzie struggled with her addiction, the affair with her father ultimately became consensual.

"I was a fragment of a person, and my secret isolated me," she writes in the new book, according to People.

"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.'

"He was completely delusional. 'No,' I thought, 'we're going to hell for this.' "

In an interview with Oprah Winfrey airing Wednesday, Phillips also lays the bombshell claim that it was her father who introduced her to the drug abuse she's battled for more than half her life, Newsday.com reports.

"My father shot me up for the first time," she says in a promotional video for the Oprah appearance. "I remember going into my room, I was crouched on the floor. ... He put the needle in my arm and put the plunger in and he missed," she says. "He missed the vein and my whole arm went numb."

Her latest scrape with the law came in October 2008, when the actress pleaded guilty to drug possession after being arrested at Los Angeles International Airport with needles, cocaine and heroin. A judge ordered her into a drug rehabilitation program.

Mackenzie also starred in "American Graffiti" and, more recently, on the Disney Channel show "So Weird." She also made guest appearances on the TV series "7th Heaven," "Cold Case" and "NYPD Blue."