Mackenzie Phillips Seeks to Clarify Incest Issue

09/24/2009 AT 02:30 PM EDT

Mackenzie Phillips wants the world to know her father, 1960s musician John Phillips, "was not a bad man, he was a very sick man," burdened by the legacy of his own troubled childhood. Yet the sexual relationship between the two of them that she writes about in her explosive new memoir, High on Arrival, began when her dad raped her at age 19 and was certainly not an "affair," as some media have categorized it.

"He didn't set out to hurt me," the former One Day at a Time child star, 49, told Meredith Vieira on Thursday's Today show. "He did the best with what he had. He was a damaged guy."

While "Papa John" of the Mamas and the Papas group died in 2001 from the effects of alcohol and drug abuse, surviving members of his family – particularly his ex-wife Michelle Phillips – have voiced doubts about Mackenzie's claims in her new memoir, High on Arrival.

"Mackenzie has a lot of mental illness. She's had a needle stuck up her arm for 35 years. She was arrested for heroin and coke just recently. She did Celebrity Rehab and now she writes a book. The whole thing is timed," Michelle Phillips, 65, said in a quote published by Roger Friedman of

"Mackenzie is jealous of her siblings, who have accomplished a lot and did not become drug addicts," Michelle told NBC.

But Mackenzie's half sister, Chynna Phillips, backs up the author, saying that Mackenzie's tale of drug-fueled incest is too incredible to have been imagined.

Another sister, Bijou, and her brother, Tamerlane, have shown measured support, according to NBC.

On Today Mackenzie said that as far as she knew her sisters were not abused by John Phillips. As for the family reaction to her revelations, "If you open a textbook on incest you can see a picture of the Phillips family," Phillips said. "We are behaving in a typical way. The instinct is to say it’s not true. The instinct is to deny. The instinct is to brush it under the table. The instinct is to protect the abuser.

"I love my family," she continued. "I understand this is very difficult, and to be revealed on a public level such as this makes it ever more difficult, and my heart goes out to them. I know that, God willing, as a family we will all be stronger when this dies down."

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