* Economist Jim O'Neill to head new antibiotics panel
* Antimicrobial resistance discussed at recent G7 summit
* Cameron warns of return to "dark ages" in medicine
LONDON, July 2 (Reuters) - Prime Minister David Cameron called on Wednesday for global action to tackle the threat of drug-resistant superbugs and said Britain planned to take a leading role in finding ways to spur the development of new antibiotics.
A world without effective antibiotics would push medicine back into the "dark ages", he said, with routine surgery, treatments for cancer and organ transplants potentially becoming impossible.
Cameron announced an independent review led by former Goldman Sachs chief economist Jim O'Neill to pinpoint the problems and identify why so few new antibiotics are being developed.
O'Neill will bring together experts from around the world, reflecting the global nature of the superbug threat.
Cameron said he had discussed the issue at a G7 summit of leaders in Brussels last month and had won specific support for the initiative from U.S. President Barack Obama and German Chancellor Angela Merkel.
"This is a very serious threat. We are in danger of going back to the dark ages in medicine, to see infections that were treatable not be treatable," he said in BBC interview.
"We have to grip it globally because this is a problem that will affect every country in the world and Britain is providing leadership to make that happen."
The O'Neill Commission will be hosted and funded by the Wellcome Trust charity, which is contributing 500,000 pounds ($850,000) to the project.
Drug resistance is driven by the misuse and overuse of antibiotics, which encourages bacteria to develop new ways of overcoming them.
Resistance has been a feature of medicine since Alexander Fleming's discovery of the first antibiotic, penicillin, in Britain in 1928. But the problem has become worse in recent years as multi-drug-resistant bugs have developed and drug companies have reduced investment in an unprofitable field.
Unlike big sellers such as statins for lowering cholesterol, antibiotics are used for only short periods and doctors also tend to keep the newest and most potent ones in reserve.
Prices for antibiotics are also low, reflecting the availability of many cheap generic versions, in contrast to treatments for other diseases such as cancer.
RACE AGAINST EVOLUTION
Recent years have seen the emergence of strains of infections, including tuberculosis, malaria, pneumonia and gonorrhoea, that resist all known drugs.
Only a handful of new antibiotics have been developed and brought to market in the past few decades, and it is a race against time to find more as bacterial infections increasingly evolve into superbugs resistant to even the most powerful last-resort medicines reserved for extreme cases.
One of the best known superbugs, MRSA, is alone responsible for tens of thousands of deaths in the United States and Europe, as well as untold numbers in poorer countries.
Cameron's decision to set up the O'Neill Commission follows a call by scientists in May for a independent body on antimicrobial resistance, modelled on the Intergovernmental Panel on Climate Change.
In one promising sign, Swiss drugmaker Roche recently said it was returning to the antibiotic field - but its move runs counter to a gradual drift to the exit by Big Pharma over the past decade.
Only a handful of pharmaceutical firms with large antibiotic R&D programmes remain, compared with nearly 20 in 1990, according to the Infectious Diseases Society of America (IDSA).
($1 = 0.5877 British Pounds) (Editing by Mark Potter)