A report into England's most troubled families has painted a grim picture of sexual abuse and welfare dependency going back generations as part of a "legacy of trouble."

In many households violence is endemic and "entrenched cycles of suffering problems and causing problems" poisons whole social networks, according to David Cameron's troubled families tsar Louise Casey

Casey, who has been tasked with turning round the lives of the 120,000 most dysfunctional by 2015, conducted more than a dozen in-depth interviews to compile her report on the challenge the Government faces.

She found that experiences were often passed from generation to generation, such as domestic and sexual abuse, teenage pregnancies, police call-outs and educational failure.

"The prevalence of child sexual and physical abuse and sometimes child rape was striking and shocking," the report said.

"It became clear that in many of these families the abuse of children by in many cases parents, siblings, half-siblings and extended family and friends was a factor in their dysfunction.

"Some discussed it as if as it was almost expected and just a part of what they had experienced in life. Children often had not been protected by their parents.

"In many of the families the sexual abuse repeated itself in the next generation... There were also incidents where families talked about incest."

Other common themes included people having children very young, and large numbers of them - often with different partners.

The report backed tackling the inter-linked issues of a whole family, rather than dealing with single problems or single individuals within a household.

Ms Casey said: "I am not making excuses for any family failing to send their kids to school or causing trouble in their community. However unless we really understand what it is about these families that means they behave in this way, we can't start to turn their lives around.

"Conducting these interviews has been an eye-opening experience - to hear first hand about the lives these families lead and the legacy of trouble that's often been passed down to them.

"It is clearer than ever to me now that we cannot go on allowing troubled families to fail their children; none of the parents I spoke to wanted their children to repeat a life of chaos and trouble, but often they couldn't see how to put things right by themselves - they needed practical and persistent help to do so."

Speaking to the Guardian, Casey outlined the depth of the problem: "It's not just that you are a family and your kids are antisocial, and it's not just that you started having five to 10 children from the age of 16. It's every single problem going ... they are responsible for a good number of them and some of [them] feel they don't need help from anyone."

Communities Secretary Eric Pickles said: "I welcome this report as an important part of that process as it provides a real insight into these families' dysfunctional lives.

"My civil servants are not just sitting in an office in Whitehall telling local authorities what to do but seeking to gain a true understanding of the challenges they face."

The Government has promised to pay upper-tier local authorities up to £4,000 per eligible family for reducing truancy, youth crime and anti-social behaviour, or putting parents back into work.

The programme's £448 million three-year budget is drawn from across seven departments in a bid to join up local services.