Tens of thousands of diabetics in poor countries have been switched to expensive new medications that have no additional clinical benefits as a result of lax international regulations, new research warns.

Post-marketing studies for insulin analogue drugs have left thousands of poor patients in India on treatment which costs eight times the amount of generic drugs which are just as effective. This means some patients are spending a third of their household incomes on medications with catastrophic consequences for their families, according to John Yudkin, emeritus professor of medicine at University College London.

The research comes after an investigation by The Independent last year revealed some devastating consequences of the globalisation of drug trials.

The diabetes patients, who in low and middle income countries generally pay for their own medications, are recruited by doctors paid by the drugs companies for every person they enlist onto the observational study. In developed countries like the UK, France and Germany, the National Health Service or insurance companies foot the bill.

The three papers, published in the British Medical Journal, call for much tighter regulation of post-marketing studies, which they claim are being used by drug companies for predominantly commercial a nd not scientific reasons.

These studies, which are meant to test the drug in real-life settings, are subject to far fewer rules and less rigorous monitoring than the controlled clinical trials. The drug companies deny that observational studies are being used for marketing purposes.

Professor Edwin Gale, emeritus professor of diabetic medicine at the University of Bristol, who analysed the post-marketing studies of insulin analogues carried out by three drug companies involving 400,000 diabetics worldwide, said there was little evidence of benefit for the patients or medical knowledge.

Furthermore, the costs and hassle of changing a patient's medication means most were likely to remain on the newer, more expensive drugs regardless. The rules are tighter in the United States than in Europe, where far fewer such trials are conducted, the study found.

Professor Gale said: "Since marketing can be guaranteed to expand in any direction that is not expressly forbidden, this type of study will continue unless tighter regulation is introduced. This should provide a much clearer definition of what constitutes a legitimate non-interventional study."

India, where more than 1,700 people are known to have died between 2005 and 2010 while participating in clinical trials for multinational drug companies, has seen one of the biggest rapid expansions in clinical trials since its regulatory system was relaxed in 2005.

The Independent's investigation last year raised serious questions about the ethical oversight and protection for patients in countries such as India. The country is one of the prime targets for companies doing post-marketing studies for diabetes drugs as with 40million sufferers it has more diabetics than any other country in the world.

In the third BMJ paper, a former researcher from a major drug company, said: "Some of the studies I worked on were not designed to determine the overall risk:... they were designed to support and disseminate a marketing message."