The reason so many new drugs are appearing is because we keep banning them. It's time for a change of approach

How easy is it to invent and manufacture a recreational drug that does not break any UK drug laws? I just spent the last two months doing exactly that – and the answer might surprise you.

Since 2008, the emergence of legal highs has wrong-footed policymakers, parents and police. These drugs imitate the effects of cocaine, amphetamines, MDMA and cannabis. They are popular, legal to take and supply, and their use is growing. Barely a week goes by without a press or TV report of a death, or major psychological consequences, as a result of using them. These reports often claim that it is a trivial task to take a banned drug and, with a little molecular trickery, get a Chinese lab to produce a new, legal version.

Most stories about legal and illegal drugs in the mass media are at best hysterical and inaccurate, and at worst simply untrue, so I decided to put this particular claim to the test.

The market in legal highs is growing. In 2009, the European Monitoring Centre for Drugs and Drug Addiction's early warning system discovered 24 new drugs. In 2010, it found another 41; in 2011, another 49; and in 2012, there were 73 more. By October 2013, a further 56 new compounds had already been identified: a total of 243 new drugs in just four years.

Or rather, make that 244, because as part of a two-month investigation for the online science and technology publisher Matter, I just devised a new, legal drug, had it synthesised in China, and delivered to a PO Box in central London. It is a close chemical cousin of a substance that was well-loved by some of the world's most famous musicians, and, it's rumoured, by John F Kennedy, Marilyn Monroe, Elvis Presley, and Truman Capote – but was banned decades ago.

There's a bag of it sat in its courier packaging on my desk as I write. There's also a sample at Cardiff University, where Andrew Westwell, a brilliant chemist at the WEDINOS project, a Welsh government-funded initiative that tracks and identifies new drugs. He has analysed it and proved its authenticity and guessed at its likely effects if taken: a stimulant.

All it took me was a few dozen phone calls to Shanghai, a gmail account, a bank transfer, a PO Box set up in a false name, a few emails to contacts on web forums that gave me the synthesis and the modification and the name of a friendly laboratory, and a bit of reading. Job done.

In its latest World Drug Report, the United Nations acknowledges (pdf): "While new harmful substances have been emerging with unfailing regularity on the drug scene, the international drug control system is floundering, for the first time, under the speed and creativity of the phenomenon."

There are now more legal drugs on sale than were even dreamed of when the first global drug laws were written: the 1961 and 1971 UN drug conventions proscribe just 234. They were written when the Beatles were still performing, in an age when the internet did not exist.

As Australian medic David Caldicott told me, "If you treated any illness with the same antibiotic for 50 years, medical people would be stunned if resistance hadn't developed." New strains and mutations call for new medicines.

So if new drugs are the problem, what is the answer?

The response of UK governments, of all stripes, has been wholly inadequate. The Conservative/Lib Dem coalition introduced Temporary Class Drug Orders (TCDO) in November 2011, which allow drugs to be temporarily controlled for a year and then banned once the Advisory Council on the Misuse of Drugs (ACMD) has pondered their harms.

This law has done nothing to slow down chemical innovation. Since the NBOME-series of hallucinogenic drugs was banned this summer under a TCDO, a new family of equipotent hallucinogens – about which we know even less – has come to market, known as the NBOH-series of drugs. When 6-APB, an ecstasy-like drug was banned, 5-EAPB came to market. After methoxetamine – a ketamine derivative – was banned, a distant, inbred cousin from a far-flung branch of the chemical family tree, diphenidine, has come on sale. For every synthetic cannabinoid the authorities have banned, a half-dozen more have popped up, all of which are less understood by doctors than cannabis.

There is simply no let-up. In the time it took to write my last story about legal highs, five new drugs came on the market. Each of them will be banned, as will the legal high that I have just commissioned. A new modification will fill the gap within days.

It is not an especially simple or trivial matter to untangle the UK's drug laws and find a drug that can be sold legally, but it can be done with a little effort, as my investigation showed. It can, however, be a hugely profitable affair. Who cares about the consequences for users' health? Certainly not the vendors of these drugs, who dodge the law by saying they are not for human consumption.

The real issue is this: we are confusing cause and effect. The reason so many new drugs are appearing is precisely because we keep banning them. That approach worked in the 1960s and 1970s, and even perhaps until the 1980s. But in the internet era, it is impossible to control this market. More laws equals more drugs. If I, a journalist who until recently knew nothing of chemistry, can commission a new drug in a matter of weeks, so can many more people. And they will.

Policymakers' prime concern should not be which drugs are legal or illegal, but which are the most harmful. Their next problem is how to regulate the market in psychoactive chemicals. That will be more complicated than anyone – even those who advocate radical new approaches, including decriminalisation – dare consider.

• You can read Uncontrolled Substances, Mike Power's investigation into the past, present and future of the designer drugs scene, for $0.99 (60 pence) on the science and technology site MATTER © Guardian News and Media 2013