Josef Fritzl, the Austrian engineer who kept his daughter in a dungeon under his house for 24 years, would often spend the whole night with her and the children she bore him, his sister-in-law has said.

In the first interview by a member of his extended family, the woman, named only as Christine R, 56, said that Mr Fritzl made daily visits to his cellar on the pretext that he had work to do and would tell other family members, including his wife Rosemarie, not to disturb him.

“Sepp [Josef’s nickname] would go to the cellar every day at nine in the morning and he would often even spend the night there. Allegedly, to draw blueprints for the machines he was selling," she told the Oesterreich newspaper.

"Rosi was not even allowed to bring him a cup of coffee."

Commentary: a society that nurtures secrets

What society would accept the probability of three children being left on the doorstep of Josef F and grant him adoption?

Multimedia

• Pictures: house of horror

BACKGROUND

• Why are child abuse scandals happening in Austria?

• Analysis: damage caused may never be healed

• Brutal double-life of Josef Fritzl emerges

• Police search other Fritzl properties in Austria

Related Links

• Could the Fritzl case happen here?

• World of fairytales hid dungeon's reality

• Police flounder as Fritzl clues suggest accomplice

Multimedia

• Video: how Fritzl led a double life

Mr Fritzl, 73, fathered seven children with his wife, including Elisabeth, now 42, whom he enticed into the cellar under his home in Amstetten in 1984 and held captive for more than two decades.

He has confessed to having fathered a further seven children with his daughter as he lived an amazing double life that authorities never suspected, despite a rape conviction in the late 1960s.

Mrs R told the newspaper: “I was 16 when he was imprisoned for a sex offence. I found it truly disgusting, especially since he already had four children with my sister by that time.

"I have always hated him. He was born a criminal and will die a criminal”

Meanwhile, an yet unnamed woman from Linz who was allegedly raped by Mr Fritzl has come forward and is planning to publish her account in a local newspaper.

The development will undermine Austrian authorities’ claims that it would be difficult to find out whether Mr Fritzl had previous convictions because of the practice to destroy records about sex offences after only ten years.

It will also embarrass social services, who allowed Fritzl to adopt one of his daughter's children and become the official foster parent of two others.

Mrs R told Oesterreich: “At the time [of the rape] he worked in Linz a lot and would spend the night there. He would ride on a bicycle at night and clearly he climbed to the first floor flat of that woman [the rape victim].

She gave further details about Mr Fritzl's "despotic" behaviour with his first group of children, who are all now grown up.

She said: “He heaved like a drill instructor with his children. They had to stop whatever they were doing and stand still when he would enter the room - even if they were in the middle of playing some game.

“They constantly feared punishment. The only way to escape that surrounding was to get married. And they all did that, as soon as they were old enough.”

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