The team, led by journalist and writer Robert Cockburn, suggest that the reluctance is "apparently motivated by the belief that the publicity will harm the sales of brand-name products in a fiercely competitive business."
They have published the findings of an investigative report in the open-access health journal PloS Medicine which suggest that up to 15 per cent of all drugs sold worldwide - worth of $35 billion (€25bn) - are fakes. This estimate - based on communications with regulatory authorities, is more than twice the 6 per cent figure put forward by the World Health Organisation.
Moreover, in parts of Africa and Asia, the situation is even more serious, with over half of purchased drugs fakes, according to the authors.
"The estimated 192,000 patients killed by fake drugs in China alone in 2001 gives an indication of the health consequences of counterfeiting, they say, while the recent discovery of fake HIV medicines in Central Africa "raises the prospect of a disastrous setback in the treatment of AIDS in sub-Saharan Africa, unless vigorous action is taken now.
Cockburn and his fellow authors - who include tropical medicine experts Prof Nick White and Dr Paul Newton from Oxford University in the UK and Mahidol University in Thailand, as well as drug regulators Dr Dora Akunyili of Nigeria and Kyeremateng Agyarko of Ghana - will present their provocative findings at the second Global Forum on Pharmaceutical Anticounterfeiting later this week.
The problem is enormous, say the authors. For example, in December of 2000, Belgian customs seized 57,600 packs of fake Halfan (halofantrine) capsules, an antimalarial sold by GlaxoSmithKline - en route from China to Nigeria. The counterfeiters in China were preparing to export 43 tons of counterfeits of 17 brands of drugs from seven international pharmaceutical companies.
Pharma 'keeps the problem quiet'
Although drug companies have sometimes voluntarily issued public alerts when they have discovered that their drugs have been counterfeited or tampered with, Cockburn said that they have not found one country where companies have a legal duty to report such discoveries to public-health or trade authorities.
Professor White said: "The production of sub-standard and fake drugs is a vast and under-reported problem and seems to be increasing. It causes unnecessary deaths and illnesses and a loss of confidence in medicines. The pharmaceutical industry is a big benefit to our health but it is harming patients and itself by not warning the public of fake products when they arise."
Cockburn believes that the suffering of millions of patients could be eased by issuing public health warnings from available information that is currently kept confidential by the pharmaceutical industry.
"Our report urges a change to mandatory reporting by drug companies to governmental authorities, which should also have a legal duty to investigate, issue appropriate warnings and share information across borders."
The key to combatting counterfeiting resides in the provision of effective, available, and inexpensive drugs, proper enforcement of drug regulation and more openness from governments about the counterfeit problem. Also crucial is more effective policing against counterfeiters and their corrupt allies in government and industry, as well as enhanced education of patients, drug sellers, and health workers.
The article can be read in full on PloS Medicine's open access website here.