Lordy…just when you thought this story couldn’t possibly get any more nauseating…In an interview on The Oprah Winfrey Show Wednesday, former One Day At A Time child star Mackenzie Phillips revealed that she not only carried on a consensual incestuous affair with her own natural father for a decade, she once feared she was pregnant with his child….

Mackenzie says her sexual relationship with Mama And Papas legend John Phillips began when she was 19, on the eve of her wedding. It ended in the late 1980s, after she became pregnant and didn’t know whether she and her unborn child shared the same father. Mackenzie had an abortion, which her father paid for, “and I never let him touch me again.”

No wonder she’s always high.

During today’s show, Oprah read a statement from Genevieve Waite, mother of model Bijou Phillips and John Phillips’ wife at the time of the alleged abuse, says he was “incapable, no matter how drunk or drugged he was, of having such a relationship with his own child.” John’s second wife, Mamas And Papas singer Michelle Phillips also refuses to believe her ex-husband could be responsible for such a crime. “You should take with a grain of salt anything that’s said by a person who has had a needle stuck in their arm for 35 years. The whole story is disgusting.”

John Phillips died of heart failure in 2001. He was 65. Mackenzie says she forgave her on his deathbed, but she had to go public with their affair to help others.

“I can’t be the only one this has happened to,” she told Oprah. “Someone needs to put a face on consensual incest.”

Mackenzie’s memoir, High On Arrival, hit booksellers’ shelves today.