Mackenzie Phillips says she had sex for years with her father, John Phillips

Mackenzie Phillips’ family secret is a secret no longer.

In her spill-all autobiography, "High on Arrival,” she details her memories of drugs, sex, rehabs, arrests, and divorce. But the topper is her confession of a longtime incestuous relationship with her father, John Phillips, which started – she thinks – in 1979.

That year, on the evening of her marriage to Jeff Sessler, son of Freddie Sessler, a longtime member of the Rolling Stones' entourage, she writes that her dad showed up, determined to stop the wedding.

Phillips, just 19, recalls in her book: "I had tons of pills, and Dad had tons of everything too. Eventually I passed out on Dad's bed."

She explains in her book that her father had "no 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," she writes. "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."

In 1980, her constant drug use got her fired from “One Day at a Time." So she went to rehab – with her dad.

By this time, she then became more than his consensual sexual partner, she was also in his band, touring as part of the New Mamas and the Papas.

Her dad even talked about them moving to a country where incest was accepted.

"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."

Will you buy Mackenzie's book? Should she have shared this secret outside of a therapist's office? Is she courageous or foolish to put this out there?

John Phillips, having had a liver transplant in 1992, joked to Howard Stern about drinking again a few months after the organ replacement surgery: "I was just trying to break in the new liver." He died in 2001 of a heart attack at age 65.