Making up counterfeit anti-impotence pills can be as much as 2,000 times more profitable than dealing in hard drugs, according to one expert.
With millions of potential buyers available on the internet, the trade is also less risky for gangsters.
But there were warnings that the fake blue pills, often made from a cocktail of prescription medicines, can be highly dangerous for users.
Last months a report in Singapore highlighted that four men died and three were left in comas in just five months after taking counterfeit impotence drugs.
Jim Thomson, founder of the European Alliance for Access to Safe Medicines (EAASM), said that the prospect of high profits was now attracting criminals into the fake Viagra market.
"You can buy a kilo of the active ingredient of Viagra on a website for about £33 and you can make a lot of tablets from a kilo," he was quoted as telling the Daily Star.
"The margin is about 2,000 times more profitable than cocaine."
He went on: "If you bought a kilo of cocaine in Bogotá you would be lucky to get out alive, if you were caught you would go to jail for a very long time.
"With the pills you would be very unlucky to get more than three years if you got caught."
But he said the bogus pills were "illegal in every way" and potentially dangerous.
