Danniella Westbrook is luckier than she knows

If she had not been able to pay for rehab, like many addicts she could be selling her body for drugs by now

Here's a great idea for a TV show: let's take a fragile recovering coke addict who's just had her septum restored (it was eroded away by the constant coke use, you see). And let's dump her in the middle of an Australian jungle with a horde of weird egotists and a pair of unnaturally cheerful Geordie midgets, bombard her with insects and rats, and watch her go mad! Sounds cruel? It's nothing compared with the way we treat most drug addicts in this country under our current failing system of drug prohibition.

Danniella Westbrook is currently enduring a week on I'm A Celebrity, Get Me Out Of Here!, watched by 10 million of us. (She seems only marginally less miserable than in her former life on EastEnders, where her character, as I recall, seemed to run away to Spain on an abnormally high number of ocassions.) But the blunt truth is that if she had not been lucky enough to have the wealth to pay for private rehab, she would probably be reduced to the state of most female Class A drug addicts in Britain: selling her body on the streets in a desperate bid to feed her addiction for the next week, day, hour.

In a country with a population of 58 million people and between 250,000 and 500,000 problematic Class A drug-users, we have 3,000 rehab places available on the NHS each year. That is not a misprint. 3,000 places – which works out as one rehab place per 83 to 166 addicts. I cannot find a single expert on our current drugs policies who believes that Danniella would have ended up in one of these extremely limited slots. This is because she was not involved in theft, most of our treatment places are designed for opiate users (despite the advice of the World Health Organisation), and she has two young kids (places that can accommodate women with children are even more hard to find).

Without an EastEnders-enhanced bank account and a millionaire husband, Danniella would have been left to the vagaries of underfunded detox programmes "in the community". As she tried to stop, she would still have been surrounded by her coke-using friends and temptation at every turn; the chances of succeeding in weaning herself off would have been slim.

The repercussions of this policy are massive. Tiggey May, a senior researcher at South Bank University, studies British prostitutes. She explains: "A huge number of the women I meet on the streets want to go into rehab, but they know that finding a place is extremely difficult. The proportion of addicts who are women is increasing, but mother and baby units haven't been created at anything like the same rate, and most women don't have somebody they can just leave their children with... A majority of the women working on the streets are crack addicts, but they don't get the support to change their lives that they badly need."

And it's not just the women themselves, the countless lost Danniellas whom nobody watches on prime-time TV and nobody notices, who suffer: it's you and me. A Home Office-commissioned study last year found that the economic and social cost of Class A drug use add to an amazing £10.1-17.4bn a year – and 88 per cent of that spending goes on crime. Half of all property crimes, according to Home Office Minister Bob Ainsworth, are caused by addicts. Every second theft, then, is a consequence of the failure of the government to invest in rehab: remember that next time you come home to see your door broken open and your valuables gone.

If ever there was an example of where "tough on crime, tough on the causes of crime" could be put into practice, this is it. The long-term savings – for police and court time and government money – involved in providing rehab are massive, and the political capital waiting to be seized in a country terrified of crime is vast. If the Government needs an easy source of revenue for funding this massive crime reduction programme – one of the few methods which has been shown time and again to work – they could legalise and tax the vast and unstoppable drugs trade that already exists in this country. Drug-dealing happens every second of the day, and only the most blinkered authoritarians now think that it can be stomped out through "crackdowns". It is only a misplaced fear of public opinion that stops the Blair government – which does not consist of fools – from admitting this.

They know perfectly well that the country that has most vigorously tried this kind of drugs repression, the US, has ended up with the biggest drug problem of all developed nations.

Meanwhile, the country that abandoned this policy soonest and opted instead for funding rehab and harm reduction, the Netherlands, is seeing its junkies age without a large younger generation to replace them.

(It is worth bearing in mind that the US drug war is now being fought by a President who has himself tacitly admitted that he has used cocaine, a crime for which he is happy to send others to jail for 20 years.)

There is a myth that those of us who campaign for drugs legalisation would happily see the whole country descend into an opium-induced trance. The defenders of prohibition conjure up a post-legalisation dystopia: one year after drugs are legalised, they imagine, heroin-injecting housewives will lie in a blissed-out sleep in Britain's gutters next to shaking, cocaine-hungry bank managers. The whole of Britain would become an omnibus edition of I'm A Celebrity....

This is absurd. I defend the right of individuals to use drugs recreationally and in moderation, and this is possible with both cocaine and heroin. (The British Government backs this in one sphere at least: US pilots and soldiers fighting alongside "our boys" in Iraq have been given amphetamines to sharpen their concentration. Why soldiers and not, say, journalists?) But crucially, just as I support and occasionally enjoy limited drug use, we legalisers also see reducing the number of addicts as absolutely central to our agenda.

There is no contradiction here: it is far easier to fight addiction when drugs are in the open, carefully regulated and sold in pharmacies (thus bankrupting all drug-pushing). Most important, under legalisation – which will happen in a European country in the next few decades, I am sure – we will have huge sums of money that would go not into the bank accounts of criminals (as it does today) but into a flowering of well-funded rehab projects across the country. Drugs legalisation and reducing the number of drug addicts are not opposing goals: they are as firmly linked as Siamese twins.

It is the supporters of the current system who are not serious about fighting drug addiction. They prefer to cling to the discredited myth that the supply of drugs can be stamped out by plugging every port and coastline on this island, and that we can carry on spending a pittance on rehabilitation.

So if you think Danniella seems to be cracking up out there in the Australian rain forest, spare a thought for all the other women with drug problems who lack her advantages in life. It is the prohibitionists – who refuse to tax the drug trade and spend the money this would raise on rehab – who are inflicting this living nightmare upon them.

j.hari@independent.co.uk