Kathy Gyngell is Research Fellow at the Centre for Policy Studies.

From the relentless pro-drugs legalisation media blitz of the last few weeks, you’d think this was the most pressing item on the government’s agenda after the floods crisis. It is not. Who is behind this campaign with a Gantt chart on their wall logging the daily media hits is a question for another day.

My worry is why responsible people are lending their names to this “cause” when they are so obviously ignorant of the facts and the implications. I am not bothered about Russell Brand. His petition demanding a parliamentary debate has become the stuff of comedy given his earlier public strictures on ignoring democracy.  Beyond celebrity groupies and metropolitan admirers, his erratic and self-serving ramblings won’t persuade.

No, the people who perturb me are middle-aged political converts to this ‘cause’ – Nick Clegg, Nigel Farage, Daniel Hannan and Norman Fowler. Whether intentionally or not, they have aligned themselves in a culture war which pits the liberal against traditionalist, cosmopolitan against parochial and old against young. This is what drugs’ legalisation is about: a war over fundamental values. It is not a battle about basic freedoms – far from it. Drugs enslave.

I doubt whether any of these politicians are or were ‘recreational’ drug users, let alone former addicts; or that they’d wish drugs on their children. Yet they’ve been persuaded that a hypothetical taxed and regulated system – one they’ve been told would cut police and prison costs, undercut criminal gangs and end the war on drugs to boot – would sanitise drug use.  It wouldn’t.  It would normalise it.

Daniel Hannan, the normally sceptical Conservative MEP is the most recent convert. ‘Do you want your children to take drugs?’ is the wrong question to ask, he says. Many would beg to disagree. Having dispensed with children, the crux of his case is that, “most quantitative analyses conclude that (drug) legalisation would bring net advantages”.

He is right that a number of economic analyses commissioned and published by pro- drugs lobby groups claim this by computing the fiscal costs associated with existing laws.  He is wrong if he thinks they address and estimate the full costs of legalisation. Quite simply the data required for a formal cost-benefit analysis is not available.

As the authors of the report that so impressed him admit, theirs are “subjective indications […] some of which should be regarded as illustrative calculations rather than formal estimates.”

The social and economic costs of departing from current policy – whether bearing on public health, mental health, education, productivity or crime (including drug driving) policing, wide scale drug testing or bureaucracy – are all unknowns. Estimates of increased use vary between 75 percent and 289 percent after legalisation, more if advertising is permitted.

Invoking fiscal rhetoric to advance legalization, like Hannans’s frankly barmy call for a temporary 12-month suspension of the drugs laws starting with cannabis, is not just deceitful, it is downright irresponsible.

I can only assume that he is unaware of the consequences of Brixton’s cannabis decriminalisation experiment and of the later temporary nationwide declassification of cannabis.  I guess he does not know that immediate rises in consumption of 25 per cent and 30 per cent took place; nor how long it took for analysis of this to reach the public domain.

I doubt he knows of Kelly and Rasul’s [2013] testing of the wider impact of the Brixton experiment. Their key finding was a dramatic rise in hospital admissions of 15-34 year old Class A drug users. They were 40-100 per cent more likely to be admitted during the policy trial – a period in which police were sanctioned to ignore street level cannabis offences.

But like the pro-legalising think tank head I sat next to at dinner recently, I suspect Mr. Hannan’s grasp of the drug problem is pretty limited. My dinner companion typically had no idea how marginal an activity drug use is compared with smoking and drinking – living as he does amongst London’s metropolitan liberals.

He was surprised that fewer than three per cent of adults smoke a spliff on any sort of regular basis compared with the 20 per cent who smoke daily and the overwhelming majority who regularly drink alcohol. He had no idea that cannabis use overall had declined in the UK, and so markedly amongst adolescents – 30 per cent in the last 15 years.

He was unaware that over the same period in the United States, when 21 States legalised so called medical marihuana, teenage drug use doubled to much higher levels than here and was accompanied by a halving of teens’ perception of harm. He knew little of the greatly enhanced cancer risks of smoking cannabis, its effects on the adolescent brain – on motivation, IQ, psychosis and schizophrenia – or that cannabis as a coroner-noted cause of death, though few, are increasing.

He rolled out the same old cliché as did Hannan: that it would be preferable, if children are to do drugs, they do them safely – quality controlled from Boots without a dealer in sight of course, and never mind their age. Not even Professor Nutt personally handing them out would make it safe, I pointed out, not after they’ve downed several vodkas and already raided their parent’s newly legal supply at home.

No matter, in their brave new world, taxation on all that pot not grown at home, and not leaked onto the illicit market, will pay for the damage done to the next generation. The irony is that Hannan and his fellow libertarians may soon find themselves on the wrong side of the culture war.

For today’s young people are more, not less, responsible than before, they drink less, use drugs less, commit fewer crimes and volunteer more as a recent Demos report shows. In these newly competitive times, the last thing this generation need is a drugs legalising experiment foisted on them by ageing libertarians.

Anyway, there already is one – in Colorado. It does not look good. According to Dr. Christian Thurstone, the director of one of Colorado’s largest youth substance-abuse treatment clinics, regular high school drug use has leaped from 19 per cent to 30 per cent since Colorado legalized medical marijuana in 2009 for adults; teens are using more higher potency products; school expulsions are up by a third, and 74 percent of teens in his drug-treatment clinic are using somebody else’s medical marijuana, all of it diverted through somebody who is 18 or older.

Since full legalisation the school situation in Colorado has got worse. “Kids are smoking before school and during lunch breaks. They come into school reeking of pot,” school resource officers say. “Students don’t seem to realize that there is anything wrong with having the pot … they act like having marijuana was an ordinary thing and no big deal”.

Mr Hannan might not mind exposing his children to this experiment.  I think most parents would.