Some of the most brutal and compelling wisdom to emerge from yet another spate of fatal violence in Britain's cities has been uttered by the grandmother of the young actor, Robert Knox. “Any idiot can have a baby,” Margaret Knox sobbed, “but bringing them up well is tough.”

The connection between upbringing and knife crime may not be constant. Nor, to many, is it as important as law enforcement. But there is little evidence that stiff mandatory sentencing, on its own, will satisfy anguished demands that something be done to end the season of killing that has taken 14 young lives this year in London alone. There is not even a clear correlation between knife crime and the number of knives in circulation, so opaque are the available statistics. Narrow prescriptions have been tried, and they have failed. They will continue to do so until combined in a strategy which acknowledges that this violence has its roots in the failure of the home.

The overall proportion of deaths caused by sharp objects is actually falling. But in the broader category of non-lethal as well as lethal knife crime, injuries are getting worse, culprits are getting younger and the fear they spread is driving many more to carry knives as status symbols and - they wrongly believe - for their own safety. Four per cent of 10 to 25-year-olds admitted carrying knives in 2005 and 1,226 under-18s were found guilty in 2007 of carrying a blade. Most did not use them, or, at worst, were mimicking the actual violence of a minority - but it is precisely this violence that has proved impervious to law enforcement.

Even as research has traced the roots of knife crime to broken families, the State has been understandably reluctant to intervene except in extreme circumstances. Not so charities such as Kids Company, founded by Camila Batmanghelidjh. The majority of the 12,000 at-risk and violent teenagers her organisation is helping come, she says, from homes with no functional parent, where chaos and often violence are the norms instead of safety, stability and relative calm.

The single most frequent cause of such chaos is drug addiction, whose devastating effect on the family the US Congress addressed a decade ago with the Adoption and Safe Families Act. Its primary purpose was to speed up the adoption of children in extended foster care. But a signal effect has been to help thousands of parents to quit drugs by giving them a firm deadline for successfully completing rehabilitation as a condition of retaining custody of their children. The act is controversial but has proved effective, and Britain has no equivalent.

Knife crime will not be defeated without a multilayered approach to match a formidably complex problem. Tougher and more consistent law enforcement is unquestionably needed. The gap between the maximum penalty for carrying a knife (four years) and the average custodial sentence (3.4 months) is absurd. But the State must be able to deter failing parents as well as errant children. A US-style deadline for drug users would bring clarity where British social workers can offer only confusion. Hard-hitting TV ad campaigns on the risks of methamphetamine abuse to families, pioneered in Montana, could also be tried here, along with intensive in-home parenting lessons offered elsewhere in the US.

Anything that attacks knife crime at its roots should be considered worth trying, because Britain's current response is not working.