Given these numerous warning signs, it is difficult to credit the latest figures issued by the Central Registry of Drug Abuse, which reveal that the total number of reported drug abusers in Hong Kong had actually decreased by 13 per cent last year (from 10,241 to 8,926) from 2013. Officially, then there are fewer than 9,000 drug abusers out of a largely urban population of 7.24 million and the most recent survey (from 2011/12) of drug use among youngsters reports "a remarkable drop in the prevalence of drug use among students across all education levels". In a widespread public consultation undertaken this year, only 43 per cent of respondents thought drug abuse was a serious problem in Hong Kong.

Professionals working on the front line of drug counselling and rehabilitation in Hong Kong are extremely sceptical about the official figures. Many are concerned about an imminent crystal-meth epidemic. Dr Vanessa Wong Ting-chi, a psychiatrist specialising in substance abuse, describes the official figures as "a joke" that reflects a "numbers game" and one experienced drug counsellor, who would prefer not to be named, says she is "shocked by the numbers" and they "do not reflect her personal experiences based on working in the field for nine years".

"The anecdotal evidence in Hong Kong … is disturbing and there clearly needs to be a wake-up call for police, medical, hospital and clinic staff, to create a coordinated effort for the prevention, intervention and treatment of this scourge," says addiction counsellor Paul Schulte.

That wake-up call appears long overdue, as concerns are being voiced privately about the quality and availability of help for those struggling with addiction and substance abuse. Some counsellors report clients being turned away from public hospitals, others fear that the predominance of Christian-based NGOs in counselling and rehab services may act as a deterrent to some sectors of society. Wong, who has years of experience in the public sector, describes services as "fragmented and even I would not know how to navigate them successfully".

Another worrying indicator is that Asia's best-known private sector drug rehabilitation centre has felt the need to open an outpatient clinic in Hong Kong; its first facility outside Thailand. Over the past four years, The Cabin Chiang Mai has been receiving hundreds of inquiries from across Asia.

"The largest number of these inquiries were from Hong Kong," says a spokesman for The Cabin, which opened a branch in Central in January.

Peter (not his real name) is a former patient of The Cabin Chiang Mai and now lives in Hong Kong. He was educated at boarding school in Britain and comes from what he describes as a stable, middle-class, expatriate family. Peter is an urbane, articulate and charming graduate in his 30s, who holds down a responsible management job in a human resources company. He is also a drug addict immersed in a harrowing daily struggle with cocaine, crystal-meth and crack addiction.

"Believe me, drugs are alive and kicking in Hong Kong - you work hard and play hard and part of playing is drugs," says Peter, who is more than aware of the destructive side of addiction. "If you just go to Lan Kwai Fong or SoHo you can see all the dealers - they are usually the Nigerians standing on the street corners. Why do you think all those African people are standing around the Buddha bar?

"Almost any of the touts outside Chungking Mansions will be able to fix you up with anything you like. It's not just copy watches you know."

Peter first connected with cocaine as a lifestyle drug in London and was introduced to methamphetamine in Singapore a few years later.

"When I came [to Hong Kong], the first thing I did was plug into drugs and line up a dealer. I was introduced by a friend to a dealer within 24 hours; you never meet them, you just get a telephone number. I send them a text saying what I want and they send it over in a taxi. They just text the taxi number plate. The whole thing takes about 30 minutes but you can order in advance if you want to," he explains.

"Predominantly, I was a solo user but it could be social, too. It could be anywhere from a friend's parent's apartment in Pok Fu Lam to a squalid crack den in Kennedy Town," he says. "Lots of expat friends who grew up in Hong Kong were exposed to drugs from an early age. That's my impression. I think kids are very exposed to drugs here and it is very accessible. Friends say they started using in their early teens.

"My wheels came off. I was into daily use of cocaine, meth and crack. I had a family crisis and I just imploded. I quit my job and my life came apart at the seams. I overdosed. I was arrested. I ended up in hospital. I overstayed my work visa, I was kicked out of Hong Kong. I couldn't even attend a family funeral because I was too high," he says, looking down at the floor.

"I had a fabulous apartment in Mid-Levels but I was living like a homeless person. I was p***ing into jam jars as I couldn't be bothered to get up and go to the bathroom. It wasn't a pretty sight, believe me. I was numb the whole time.

"Seeking help was the biggest hurdle for me," he says, and talks about the stigma of drug use and the misconception that all drug users are "weak, morally deviant or just bad". Peter hopes that his story will encourage others to seek help and says crystal meth can ruin anyone who gives into its charms.

"I have seen users of all types - it affects all strata of society," he says. "I have a lot of straight friends who use Ice; it is not only the gay community."

Schulte witnesses the tragic consequences of crystal-meth addiction in Hong Kong on an almost daily basis. His recently published book, , focuses on what he calls the "disease of secrets" in the gay community, which is a "cauldron of alcohol and drug dependence". The book charts the meteoric rise of crystal-meth addiction from California to major epidemics in London and New York.

"Everything in front of me tells me Hong Kong and Singapore are heading the same way," says Schulte, who spends about 25 hours per week working on a pro bono basis as an addiction counsellor in a number of the city's medical facilities. "Crystal meth just cleans you out; it cleans you out of your apartment, your car keys, your job, your teeth and your relationships." He estimates that about 80 per cent of his clients are young gay and bisexual men.

"Crystal meth is a drug for sex," he explains. "Its powers to allow a gay or bisexual man to leave behind the fear, shame, self-loathing and anxiety are magical."

The implication is that safe sex is often cast aside during Ice-fuelled sexual activity.

"Crystal meth leads to HIV as night follows day," he says. This link is a huge worry in a city where the chief executive of Aids Concern, Andrew Chidgey, is already describing an "HIV epidemic". The most recent statistics from the Centre for Health Protection show that 173 cases of HIV infection were reported during the first quarter of the year. If the figures for the next three quarters are the same, 2015 will have been the fifth year in a row that the number of new infections in the city has risen.

Well acquainted with the covert world of drugs and sex in the gay community, Dr Sky Lau Hoi-leung spent three years researching his controversial PhD sociology thesis "Experiencing Risky Pleasure - The Exploration of 'Chem Fun' in the Hong Kong Gay Community". He interviewed 30 subjects, or "playmates", about their drug use and sexual practices at "chem fun" parties; social gatherings where gay men chat, dance and "play" (i.e. have sex).

Lau believes that too much analysis of drug use in gay circles is shrouded in taboo, shame and an obsession with public health, driven by government bodies and NGOs dominated by the values of Christian groups.

"We don't have any official figures for the scale of the chem-fun lifestyle but it is becoming much more prevalent and much more prevailing in the Hong Kong gay community," says Lau.

Picking up his phone, he scrolls through a colourful mosaic of tiny images of bare torsos, buttocks and penises on Grindr, one of the most popular gay dating apps in Hong Kong. Even a casual examination reveals a significant number of men seeking "chilled fun", "chem fun", "plug and play" and "Tina", all well-known euphemisms for drug-and-sex parties. Some men have usernames such as cfun79 and chem90, which clearly indicate their preferences.

Lau says there was a drastic shift in 2009-10.

"The whole scene in chem-fun culture changed from Ecstasy and K [ketamine] to crystal meth; this was a consistent and universal observation reported by all my informants," says Lau.

Grindr has 2.3 million users in more than 190 countries and there are several similar apps. Hong Kong is one of the top 10 cities in terms of numbers of users, so while the scale of the chem-fun scene is impossible to measure accurately, it clearly involves thousands rather than hundreds of men in Hong Kong regularly using crystal meth as a recreational lifestyle drug.

"Most say they have a great life but they just want to have great sex," says Lau, who explains that managing the risk is part of the pleasure. He does not necessarily think these playmates are in denial about their addiction but that they wish to distance themselves from the stigma attached to a stereotypical heroin junkie.

However, "thinking that you can control your drug use is part of being an addict; only other people can see when you have lost control", says Wong, who worked at the Pamela Youde Nethersole Eastern Hospital before setting up a private practice. "Any drug that hijacks your brain is really not a good idea.

"Methamphetamine is probably the most toxic of all drugs and the quality of the product on the streets is hugely variable. When methamphetamine use goes wrong, the patient has to be physically restrained - then they will 'melt down', which means they sleep for three to four days. On waking they have no recall of what has happened. If they are lucky, there are no long-term repercussions but often they become paranoid or have hallucinations. Of all the drugs, methamphetamine holds the highest risk of psychosis - this essentially means it causes something fundamentally wrong with the wiring of your brain."

Like many others, Wong points to the unhelpful moral judgments made about those who abuse drugs and admits that even health professionals will characterise users as a "stigmatised group who are somehow weak or immoral people". Furthermore, Hong Kong's adoption of a moral framework for dealing with addiction, reflected in the high number of rehab and counselling services run by faith-based NGOs, makes the city appear critical - and squeamish.

Wong says she met a colleague in the United States who advertised his clinic on gay dating apps "but that would never happen here".

"If you stigmatise these people, they don't seek help; they will just hide away for fear of rejection," Wong says.

Schulte says many of his gay patients have been kicked out of their church groups because of their sexual orientation so are unlikely to go back seeking help for addiction, and Peter looks appalled when asked whether he has sought help from a faith-based organisation.

One of the agencies delivering drug counselling, and one of the few without direct religious links, is Hong Kong Children and Youth Services, in Tsuen Wan. Its employees have a caseload of about 280 addicts aged from 26 to 35, using ketamine, Ice and cocaine. They also report an increase in the use of crystal meth.

"Ketamine is the biggest drug seen here but the trend is quickly changing to Ice," says Cheng Ting-ting, a social worker who has been with the service for about five years.

Her colleagues introduce two former Ice addicts who are now teammates in the centre's championship-winning five-a-side football team, comprised mostly of users and ex-users from the local area. Jason Yuen Pak-hang and Cyrus Lau Pak-yui spent years being arrested and re-arrested for dealing and using ketamine, cocaine and crystal meth and were referred to rehab centres only to relapse before finally getting clean.

"All my friends were doing ketamine so if I didn't take it I would just look weird," says Yuen, who is now married and plays football at the centre to distance himself from his old social network, which is still drug dependent.

Lau says he started taking drugs when he was 13 years old and, by the age of 16, had been jailed on the mainland for drug trafficking. While incarcerated, he says, he was beaten on a daily basis.

"On the older housing estates near me, everyone is doing everything," says Lau. "Ice is very popular because it is long lasting, the girls like it for weight loss and it makes it easy for the boys and girls to have great sex."

but it is a treatable disease and denial is to addiction what oxygen is to fire," says Vernon Hartshorne, a counsellor at the Central branch of The Cabin. Unfortunately, it seems, Hong Kong is in denial.

On May 13, Secretary for Security Lai Tung-kwok advised the Legislative Council: "The decline in the number of arrests of drug abusers mirrors the decline in the number of youth drug abusers recorded in the Central Registry of Drug Abuse. This testifies to the effectiveness of the government's anti-drug strategies as well as the concerted efforts of the government and the community in fighting drugs."

Lai, who was approached to comment for this article but didn't reply, may be correct and officials do sometimes qualify their encouraging statements with concerns over "hidden drug taking", but there are enough alarming signs to suggest there is little room for self-congratulation. Many on the front line believe that if a major social disaster caused by synthetic drugs is to be averted, a radical plan is required.

In the concluding chapter of his book, titled "Cleaning under the rug", Whisson wrote: "The addict is a fairly normal person for the most part" who needed persuasion that it was both possible and beneficial to treat drug addiction. Half a century later, the sense of complacency in government is still apparent but perhaps the most consistent parallel with his observations is the refusal by society, including many health professionals, to accept that addicts do not necessarily have an acute moral failing or weakness that requires moral salvation or redemption.

The whole language of drug addiction in Hong Kong is still laced with shame, stigma and morality, which is only counterproductive, because it stigmatises those who need help and keeps the problem latent, or as Whisson put it so succinctly five decades ago, "under the rug".

BY THE SAME AUTHOR: Dr Manson; mosquitoes and a medical legacy