When we see violent crime increasing in this country and the use of guns becoming commonplace, we tend to call for tougher action through the criminal justice system. When we see a policewoman being coldbloodedly gunned down in the line of duty or a banker being knifed to death in his own home, we are thankful that such incidents are rare and that they do not often impinge on our generally comfortable lives. What we rarely do, however, is look at the root causes of this rise in criminality and violence and ask whether we are doing enough to stop it.

At the end of the 1980s, a decade of rising prosperity, Charles Murray, the American sociologist, offered a stark warning. In a series of pioneering articles in The Sunday Times he warned of an emerging underclass in Britain operating outside society’s norms. That underclass, he predicted, would one day be as large, as a proportion of the population, as that which had begun to emerge in America 15-20 years earlier.

Revisiting his research recently, Mr Murray offered this description: “Britain has a growing population of working-aged, healthy people who live in a different world from other Britons, who are raising their children to live in it, and whose values are now contaminating the life of entire neighbourhoods — which is one of the most insidious aspects of the phenomenon, for neighbours who don’t share those values cannot isolate themselves.”

Today we carry a piece by Shaun Bailey, who was brought up by a single mother in a mainly black working-class environment on the North Kensington estates in west London. He “escaped” by getting a university place but on returning as a voluntary youth worker was alarmed by what he discovered. “The level of crime on the estates was already astonishing but over the past four years the level of violence with drugs, guns and knives among the younger kids has got much worse,” he writes. Teenage pregnancy is rife, parental authority almost non-existent. His account matches Mr Murray’s description of the underclass phenomenon. Not only is crime routine and increasingly violent, but the peer pressure to join in is overwhelming.

For young people growing up on these estates, the economic calculation is straightforward. First, they are almost unemployable through truancy and drug abuse. If they do get a job, it will be unskilled and low-paid. The alternative is a life of easy money acquired through burglary, mugging and drug dealing. The underclass has generally existed cheek by jowl with affluent areas. So it is with the North Kensington estates, a short distance from some of the most expensive housing in Britain. It is a combination that offers an almost guaranteed recipe for crime.

Mr Bailey, whose argument is set out in more detail in a Centre for Policy Studies paper to be published this week, sees what is happening on estates such as those in North Kensington as “the betrayal of Britain’s inner-city young”. He argues convincingly that they need rules and moral guidelines. They also need role models who provide a clear link between hard work and success, not a culture of celebrity and bling. Their parents need to be encouraged and helped. What they do not need is misguided liberalism.

His alarming observation is that children are turning to drugs and petty crime, then violent crime, at ever younger ages. The boys become hardened criminals and the girls become pregnant, creating yet another downwards cycle of crime and deprivation. Those who favour decriminalising drugs should visit these estates and see their effects. There is a lesson here for those who favour a more relaxed attitude to drugs, including David Cameron, the favourite to become the next Tory leader, who himself has lived for some time just a knife’s throw from the North Kensington estates.