Los Angeles: Susan Atkins, the former Charles Manson follower who confessed to killing pregnant actress Sharon Tate during a murderous rampage in 1969, has a terminal illness and has asked for compassionate release from prison in her final days, authorities said on Thursday.

Atkins, 60, who has been incarcerated at the California Institution for Women at Frontera for 37 years, has been held longer than any other female inmate in state history.

Department of Corrections spokeswoman Terry Thornton declined to specify the nature of her illness.

"She is very ill and has been hospitalised", said Thornton. "Her condition is very serious and her prognosis is poor."

Thornton said a doctor determined that Atkins has less than six months to live, which could make the application for release futile.

Atkins was the most notorious of the three women charged with Manson in the grisly slayings of Tate and six other people in the summer of 1969. She enabled authorities to break the case after it had remained unsolved for three months by confessing to a cellmate when she was arrested in an unrelated crime. It was Atkins who disclosed that the Manson Family, a rag tag cult living in a ranch commune, had been responsible for the murders. Her statements led police to a Death Valley hideout where they found Manson and other members of his cult.