The son of the man referred to as the 'British Fritzl,' who fathered nine children by raping his two daughters, disclosed today that he had reported the matter to police and social services more than a decade ago but no action was taken.

The man, who did not want to be identified, said that he had lived in terror because of the abuse he, his mother and his sisters faced when he was a child in Lincolnshire and South Yorkshire, claiming he still has 49 scars on his head from the beatings he suffered.

The father, 56, was last month sentenced to a life term for a total of 25 rapes and will serve 19 and a half years. Sheffield Crown Court heard that his rapes had caused his daughters to get pregnant a total of 19 times.

He held his daughters virtual prisoners for 25 years, the court was told, moving them around houses in South Yorkshire and Lincolnshire to avoid detection.

Speaking for the first time about the ordeal on BBC Radio 5 Live, the son said that he had lived in terror of repeated beatings and torture until he left home at the age of 15.

However, he said did not know about his father's incestuous rapes with his sisters – and who fathered the children which resulted – until having a conversation with his mother, who at that stage had also left home, at the age of 18.

He said he told police, who reported the matter to social services – but nothing was done after he was interviewed by social workers.

"I thought it would all be taken care of – you know, when an allegation like that's put forward you'd think they'd investigate it, wouldn't you. But somehow nothing's ever got done," he said.

Asked whether he was told why no action had been taken, the son said he did not know. "(I) just left it in their hands 'cause I wasn't living at home. I mean, I was always that was in the dark. But I think something could have been done a long time ago, really."

Lincolnshire Police and Lincolnshire Safeguarding Children Board said they were investigating what happened to the family and how their circumstances were dealt with. They said they would not comment until the investigation was completed.

Also in his radio interview this morning, the son said he could not remember any good times when he was growing up, and that he and his family would feel terrified when they heard his car door slam as he arrived home in the evening.

"Once he left the house, we were free to be like normal people," he said. "But he'd come back and you could tell if he was on one because the first thing he'd do is slam his door."

The son, who is on life-long medication and mood-stabilising injections since the experiences, added that he witnessed his father beating his sisters.

"I wanted to do something, I just wasn't powerful enough," he told the BBC. "I've seen him beat my elder sister. He beat her to a living pulp one day.

"It was horrific. Just literally got her by the hair and started punching her and kicking her. She ran off to one room and he started chasing her for more punishment."

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