The 51-year-old, who cannot be named for legal reasons, started indecently assaulting his daughter when she was eight and later began raping her, Swindon Crown Court heard.

The daughter, now 31, gave birth to the first of the six children when she was 19.

Three of the children have serious disabilities after being born with genetic disorders.

The court was told the victim's mother was often away from the house visiting friends.

Robert Duval, for the prosecution, said the woman had begged her father to stop assaulting her, but he had used emotional blackmail in order to continue the abuse.

Mr Duval said the woman was worried her father would leave home if she revealed the abuse.

Instead she told other members of her family that the father of her first child was a central heating engineer.

Despite going on to have five more children, relatives did not press the issue of the identity of the father.

But two years ago social services workers became concerned and the woman and her father were eventually arrested last November and the children placed under a protective order.

Defending, Robin Shellard, said the father had only come to understand the horrific nature of his crime while on remand.

Mr Shellard said the man had not used physical force on his daughter.

But when the case ended on Monday, Judge John McNaught said the victim and her children would have continuous suffering because of the man's crimes.

Silent suffering

The man was told he would serve at least 10 years and be placed sex offenders register for life.

Christine Atkinson, NSPCC policy adviser, said: "Most child sex abuse is committed by family members or others already known to the child such as friends, neighbours or those in a position of authority or responsibility over them.

"Such abuse can continue for years, and sometimes into adulthood.

"Children who are sexually abused desperately need someone to turn to.

"NSPCC research shows that only a quarter of young people who suffer sexual abuse in their childhood tell anyone about it at the time."

The NSPCC has a 24-hour freephone child protection helpline on 0808 800 5000.