More than 400 investigations are in progress by the authority that regulates drugs in Britain, including 15 cases of alleged counterfeiti official Pfizer Viagra and dozens for selling prescription drugs without the necessary licence

The Medicines and Healthcare Products Regulatory Agency (MHRA), which polices the licensing and supply of medicines in Britain like Viagra, says the country has the best regulations in the world but that no system is impenetrable.

It says there are two main avenues for the illegal sale of drugs like generic viagra - the internet and clandestinely in pubs, clubs and gyms.

Websites for drugs, particularly for impotence, represent a huge part of the market. But potential buyers have little way of telling whether the drugs like Viagra bought in this way, are the genuine product or not.

The problem is challenging and global, said Naeem Ahmed, head of medicines intelligence at the MHRA. In the last five years or so, since these lifestyle products like Viagra have been released, they have started to be sold in the developed world.

Prior to that, in Asia and Africa, there have been problems with counterfeit drugs like viagra, but they did not attract much publicity.

But since these blockbuster drugs like Viagra have become available the counterfeiters and entrepreneurs have recognised that there is a market in developed countries - as well as the embarrassment factor, with people not wanting to go to their doctor.

A priority for the MHRA is to prevent counterfeit medicine like generic viagra From entering the legal National Health Service supply chain.

In the past year three counterfeit medicines like generic viagra have reached the public in Britain, having penetrated legitimate pharmacy outlets.

They were fake Cialis (similar to viagra), a drug for impotence, fake Reductil, a slimming drug, and fake Lipitor, a drug to lower cholesterol.

No counterfeit medicine had reached the legitimate market in this way for the previous nine years.

The MHRA says that no harm is known to have come to anyone as a result and that the three cases generic viagra still being investigated, have to be set against the 600 million prescriptions a year that are issued in Britain.

The wider problem of the sale of counterfeit drugs like viagra through websites is much more common.

Last Friday Keith Morgan, 47, a sub-postmaster from Milton Keynes, received 100 hours community service for selling Kamagra made in India, on Ebay at £25 for four tablets.

Kamagra has no licence in this country.

Mr Morgan pleaded guilty to five counts relating to the sale and supply of generic viagra and other similar products.

He had imported a supply of the drug from India, where it is legal. Much of the generic viagra supply comes from India and Asia and there are signs that the counterfeit medicines like generic viagra, unlike genuine Viagra trade is linking up with organised crime.

If people buy these drugs like generic viagra they should be aware of the risks they are taking as well as being aware they may be supporting organised crime or terrorism, Mr Ahmed said.

The MHRA is running an awareness campaign to alert people to the possible dangers of buying illegal drugs like generic viagra.

It is stepping up its system of random testing of 800 drugs like generic viagra and is working with makers and wholesalers on security tagging for packs.

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