Josef Fritzl, the Austrian man who kept his daughter locked in a cellar for more than two decades has told a psychiatrist he was "born to rape", blaming his tyrannical mother for his behaviour.

A report by a forensic psychiatrist which has been leaked to the Austrian press said that Fritzl, 73, believed his behaviour had been tame. "I was born to rape," he has said. "Bearing that in mind I controlled myself for quite a long time."

He added: "I could have behaved a lot worse than locking up my daughter."

The 130-page report based on six lengthy interviews between psychiatrist Heidi Kastner and Fritzl, details his destructive relationship with his mother. Describing himself as an "alibi child", Fritzl said his mother only had him to prove to her partner that she was not sterile.

He described a childhood in which he was repeatedly neglected. During second world war bombing raids, his mother would retreat to an air-raid shelter for safety, leaving Fritzl alone in the family home, he said.

From birth he said he had a problem with his urinary tract which made it extremely painful for him to urinate, a common complaint which could easily have been rectified. But his mother waited for years before taking him to a doctor, only doing so after the intervention of a neighbour.

Fritzl, who locked up his daughter Elisabeth, 42, for 24 years in a purpose-built cellar and fathered seven children by her, one of whom died shortly after childbirth, and three of whom lived with him and his wife in his house upstairs, said he had deliberately never looked his daughter in the face while he was raping her. Kastner said it had been his way of distancing himself from the situation.

He said he stopped having sex with his wife Rosemarie the same day he allegedly sedated his daughter and took her into the cellar. "Finally I had someone who was just for me," he said.

He said he believed that she would always remain with him. "I only had so many children with her so that she would always stay with me, because as a mother of six she would no longer hold any attraction for other men."

Fritzl admitted that he often punished his "dungeon family" for rebellious behaviour by turning off the light or letting them go hungry for several days.

He also taunted the incarcerated children with photographs of other children playing outside in the sun, to "show them there was another world".

Kastner, said his sexual behaviour and his need to dominate women was his way of "compensating for the defencelessness and humiliation he felt as a child".

Fritzl said that he had tried to escape from the horror of his childhood by burying himself in books, reading everything he could find which allowed him to suppress everything he could not cope with. He said his recognition that he was of above average intelligence was what finally gave him the courage to disobey his mother.

As an adult he said he had thrown himself into his work as a way of suppressing his sexual desires.

He described himself as a "volcano" who felt "torn" and had come to the conclusion that he possessed an "mean streak", and a "flood of destructive lava that was barely controllable".

It was shortly after puberty Fritzl began sexual attacking girls. He went on to break into the flat of a nurse and rape her at knifepoint at the age of 32.

In her report, Kastner said that although Fritzl had deep psychological issues, a severe combined personality disorder and a serious sexual disorder, he was sane enough to stand trial. But she recommended that he should spend the rest of his days in a secure psychiatric unit and should never be set free, arguing he would always be a danger to society.

He was said to have had a thin grasp of the gravity of his crime however after expressing a belief that he would spend his final days with his wife Rosemarie, and pleading for a short prison sentence so that he could continue running his property business which would enable him to provide for his family.

Elisabeth, her six children fathered by Fritzl, and her mother Rosemarie continue to receive psychiatric care, but are believed to have been moved from a clinic to a secret location where they are trying to learn to lead a normal life.

Fritzl is expected to go on trial in the next few months.