We want, Gordon Brown said yesterday, to punish and prevent. Note the order in which those words appear - when he entered No 10 Mr Brown was hoping to prevent, not punish. Gone was to be the fist-waving of the Tony Blair years; the ASBOs, criminal justice Bills, initiatives and ten-point plans. Young people were to be championed not chastised, heralded not harangued. Fear would be replaced with hope.

The benighted teenagers emblazoned across the front pages of every newspaper this month, stuffing knives down their trousers and scaring the pants off every nice but nervous mum, have scuppered that. As reporters scramble into scary housing estates protected by nothing but their television cameras, a turf war between the Home Office and Department for Children, Schools and Families has been fought over who “owns” youth crime.

Ed Balls, the Secretary of State for Children, Schools and Families, has tried and failed to have responsibility for young offenders moved into his department, wanting to shift the debate about teenage offending away from criminology and towards education. It is an ambition that Mr Brown still shares; but one that has simply been tempered by experience and the need to answer a hundred angry headlines.

For one approach is the terrain of the Conservatives, condemnatory and penalising, the other is more liberal turf, preferring to try to change behaviour through incentive, education and good example. But it is expensive and it takes time.

Somewhere into all this fell yesterday's Youth Crime Action Plan, an initiative straight from the TB Book of Government - an 80-page plan, some extra money and a slew of reannounced proposals. Except that this one unravelled faster even than one of Mr Blair's, with the idea of taking young criminals to hospital to visit stab victims half-announced - “one of the measures that we are considering”, the Prime Minister on Monday morning; “I have never said that,” the Home Secretary on Monday afternoon - then chewed up and spat out before the actual “plan” was even completed.

That seemed still to be being cobbled together yesterday morning, as the deadline for its publication passed and Home Office officials told me that they were “still waiting for it to be sent”. From whom, by where - who cares? This was a public relations exercise: a reannouncement of the plan for more community service in highly visible jackets, more parenting orders and youth centres, an extension of family intervention projects (FIPs), much of it repeated from the Youth Taskforce Action Plan published only four months ago.

And yet. And yet. In those projects and orders and plans, in those long-term interventions, among the acronyms - the CAFs and YOTs and YROs, the CYPPs and the CDRPs - in those long, hard grafts that produce more acronyms than headlines, lie a better chance than jail to address youth crime. David Cameron is right when he says that the presumption that you will go to prison for being caught carrying a knife is “plain, simple, clear” - as in that it produces a plain, simple, clear headline: “Jail knife yobs.”

But reality isn't plain, simple or clear and nor are the real solutions. Just as with his talk of a broken society, Mr Cameron both exaggerates and oversimplifies. The causes of crime, and of social problems, are complex and require complex solutions. Despite the national panic about social breakdown, real social failure, like the immediate effects of hard crime, is focused in certain devastated communities. Broken Britain is identifiable through poverty indicators, school exclusion numbers, mortality rates, crime figures and the like. It comes down, the Government reckons, to perhaps 20,000 “hard core” families out of an overall total of 110,000 “problem families”.

A primary school teacher can tell you which kids are likely to end up in jail. A statistician, in turn, could have told her which they would be, before they were even born. We have the data, and it is being used hard, to identify the families needing firm intervention, or the young pregnant woman who would benefit from the family nurse programme, where intensive one-to-one support is offered until the child is 2.

Amazing things are going on out there - the young man who has become a mentor because of an early intervention project, the mum-to-be off the booze and away from her abusive partner thanks to the support of a family nurse, the social misfit propped up by a special-needs teacher - and it is threatened by careless talk of collapsed societies, universal punishment and condemnation. Things are so much more complicated than that.

This month a speech by the Chief Constable of South Wales was leaked. Barbara Wilding said that the police and courts cannot provide a long-term solution to the violent gang culture that has replaced family ties in deprived parts of the country. Any policies based primarily on enforcement were “set on sand”; the focus should instead be on tackling the underlying social and economic causes. This is a senior police officer speaking, not some softie liberal.

And it is what Mr Brown implicitly recognised when, on entering No 10, he put the “Respect” agenda under the control of Mr Balls, who effectively abolished it, declaring that every ASBO represents a failure and that he hoped to live in “the kind of society that puts ASBOs behind us”. Yesterday they put ASBOs up front again in the Youth Crime Action Plan, but accompanied by parenting orders, a recognition that behind an angry teenager often lies some really bad parenting.

Despite the very different language used by politicians of Left and Right, most are approaching a kind of consensus about social problems: for instance, that they are focused on certain identifiable individuals and families in mostly hard-core areas; that the earlier and more intensive the intervention the better; that boys in particular need good male role models; that benefits ought to be a route to a job, not to permanent unemployment.

It is where these strands are broken that education ends up failing too, as schools try to pick up the pieces with pastoral and health advisers, and a blizzard of special-needs support from literacy and numeracy to emotional and social skills.

“I do sometimes wonder”, one special-needs teacher said recently, “whether we aren't offering too much understanding. When I was at school, you didn't bring your problems in with you. The teachers weren't interested in them.”

These days, as teachers know, as the police know, as even some Conservatives know, you have to deal with the FIPs and the YROs before you have a chance of getting to grips with the ABCs.

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