Actress Mackenzie Phillips has revealed that she had a sexual affair with her father, The Mamas and the Papas singer John Phillips.

Appearing on The Oprah Winfrey Show to promote her new memoir, High on Arrival, Phillips claimed she had been raped by her father in 1979 before her wedding to her first husband Jeff Sessler.

Phillips, who has a long history of drug problems, claims she and her father had been using illicit substances together before the initial incident when she was 19.

"On the eve of my wedding, my father showed up, determined to stop it," writes Phillips. "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."

The following year, after Phillips was fired from the TV sitcom 'One Day At a Time' over her drug abuse, she joined her father on tour and shared a consensual sexual relationship with him, which says made her feel empty and "isolated".

"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.'"

Phillips told Oprah she confronted her father about the initial rape years later, but he denied that it wasn't consensual. John Phillips died in 2001.

Last August, Phillips pleaded guilty to cocaine possession after being arrested at Los Angeles International Airport, and was sentenced to drug rehab.