A British father who raped his two daughters repeatedly for more than 25 years and had nine children by them has been sentenced to life in jail.

Sheffield crown court heard today how the 56-year-old, who cannot be named for legal reasons, "took pleasure" in knowing the harm he was doing to his two girls and threatened them with a "real hiding" if they refused to have sex with him.

The defendant, from Sheffield, admitted last month to 25 rapes and four indecent assaults. He received 25 life sentences and will serve a minimum of 19 and a half years.

His elder daughter was pregnant seven times by him and gave birth to four of his children although two of them died on the day they were born.

He made his younger daughter pregnant 12 times. She has five surviving children, the court heard.

The man, who called himself the "gaffer", also had a son who lived with them until his teenage years.

The victims were too frightened to tell anyone, even their mother.

Judge Goldsack, passing the 25 life sentences, said said: "The phrase 'it is difficult to imagine a worse case' is much overused and rarely, if ever, true. I am not going to say no case of rape within a family situation will ever come to light.

"But I can say that in nearly 40 years of dealing with criminal cases and 14 as a family judge the combination of aggravating circumstances here is the worst I have come across."

The two sisters started being abused at the age of eight but only realised the other was also being assaulted when they became pregnant some years later, the court heard.

Nicholas Campbell QC said: "All the defendant's children spoke of his domination over their family life. He was tall and strongly built.

"I quote him: he was 'the main gaffer', he called himself the gaffer and he liked to think that he was a hard man.

The court heard the daughters were raped every three days at times.

Mr Campbell said: "One sister would babysit the other children while the other was being raped.

"One of them did try to offer him £100 a month to stop and paid it from her child benefit. That went on for two to three months."

Apart from that the only time the defendant would stop raping his daughters was after they had either given birth or suffered a miscarriage or termination.

South Yorkshire police and Sheffield council said they were satisfied the offender has received the maximum possible punishment for his acts.

A spokesman for the police appealed for the public and media to respect the family and allow them to try to continue their lives after a trauma he "could not begin to imagine".

During the hearing Campbell told the court: "All the family were frightened of him. When they heard his car pulling up outside the house, the children and their mother ran to their respective rooms.

"His son described him as having a Jekyll and Hyde personality and that his dad had a one-second fuse and that he could flip and turn with the click of his fingers."

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.

"The sisters recall that they were kept from school when they bore physical injuries. The defendant also ensured that his family were kept isolated and that there were very few visitors to the home.

"Rather than having babysitters, the children recall being locked in their rooms when their mother and father went out.

"Even then there was speculation and talk from the neighbours about the growing family but the lack of any other men apart from the man who called himself the grandfather."

In 1988 the victims' school became suspicious about their injuries but these were blamed on bullying.

In the early 1990s the defendant moved with his two daughters, wife and son from South Yorkshire to Lincolnshire where they lived in isolated small villages.

Shortly after the move his wife left him. The father continued to share a council house with his two daughters and son but he made the teenage boy sleep on the landing outside the bedrooms he shared with his victims.

The court heard that one way the defendant prevented his children from alerting the police or social services was by telling them they would have their children taken from them. He also threatened to kill them.

His younger daughter was kicked and punched during one incident in 1998 for meeting the son of one of her neighbours.

He then attacked his eldest daughter, holding a knife to her throat, before claiming: "It's never going to end. You have to do what you are told."

The women then called Childline and asked for a guarantee that they could keep their children but when one was not offered they ended the call.

Whenever the sisters were challenged about the paternity of their children they did their best to cover it up, Campbell told the court.

He said: "They started taking the pill. He said they should not be taking it and, just as they felt unable to avoid his sexual abuse, they obeyed.

"They spoke of his pleasure at fathering their children whilst at the same time they had fears for the welfare of these children and how they would cope."

In 50% of cases where a father and child or brother and sister have a baby, severe illness, premature death or learning disabilities will occur.

The court heard that on a number of occasions doctors advised the women to stop having children by the same father.

At one stage towards the end of the abuse, the defendant offered his younger daughter £500 to have another child with him.

The court heard that they tried to give their father as much whisky as he wanted so he would drink himself to death. But it was not until last summer that the younger daughter managed to flee her father's grasp.

The case is already being compared with the Austrian rapist Josef Fritzl, who kept his daughter locked in a dungeon for 24 years as he fathered seven children with her.