The case has disturbing parallels with that of Austria's Josef Fritzl, who fathered seven children with the daughter he locked in a dungeon for 24 years. While Fritzl is still awaiting trial, the Sheffield man was on Tuesday ordered to serve 25 life sentences behind bars.

His daughters, whose identities remain secret, expressed relief that their harrowing ordeal was now over. "His detention in prison brings us only the knowledge that he cannot physically touch us again," they said in a statement. "The suffering he has caused will continue for many years and we must now concentrate our thoughts on finding the strength to rebuild our lives."

Sheffield Crown Court judge Alan Goldsack said the case was "the worst I have come across" in nearly 40 years. "I have little doubt that many members of the public hearing the facts of this case will consider either you should never be released from prison or only when you are old and infirm," he said as he handed down his sentence to the man, who had refused to leave his prison cell to attend the hearing.

"I agree with that view." The man, a self-employed businessman who liked to call himself the "gaffer", was arrested after social workers learned in June about the decades of abuse his daughters suffered. During a hearing last month, he admitted 25 rapes and four indecent assaults.

The court heard the abuse began when the man's daughters were aged eight and 10 and that he "took pleasure" in the harm he knew he was doing to them. The elder sister fell pregnant seven times, the younger 12 times.

Of their 19 pregnancies, 10 babies were lost because of miscarriage or abortion, while two died on the day they were born. Prosecutor Nicholas Campbell, QC, said that, when either of the sisters tried to end the abuse, their father threatened to kill them and their children. They tried offering him £100 a month from their child benefits to stop the abuse and tried to give him as much whisky as they could in the hope he would drink himself to death.

To ensure the abuse remained secret, the man repeatedly moved house with his family, including his wife and son. His wife left in the early 1990s. "All the family were frightened of him," Mr Campbell said.

"His younger daughter told of the frightening habit her father had of putting her head next to the flames of their gas fire and that, when she struggled to get away, on certain occasions she burnt her eyes." In 1998 one of the sisters called a helpline run by the charity Childline and asked for a guarantee that she could keep her children if she came forward about the abuse. But no guarantee was granted and the sisters' suffering went unreported.

Police and social services have launched an independent review into the case and why the abuse was not detected sooner. Ian Keates, for the Crown Prosecution Service in South Yorkshire, described the abuse the sisters had been subjected to as "beyond comprehension".

"In his treatment of his victims the defendant sank to the most profound depths of depravity," he said. AAP