Pfizer Netherlands has started a radio campaign against Viagra spam, warning consumers that 97 per cent of the pills offered are counterfeit.

Radio commercials on public broadcast radio and Sky Radio also warn purchasers that many of the illegal drugs are unapproved and may not contain the real chemical.

Pfizer is citing a report by the Dutch National Institute for Public Health and the Environment (RIVM), which says that falsifications are a risk to public health. Many of the pills are produced without adequate quality control, although the pills and the packaging can appear to be the same.

Some rogue pharmacies claim to sell "legal generic Viagra", which doesn't even exist, as Pfizer's patents are still in place. Others claim the drug meets World Health Organization (WHO) standards, although the WHO does not ensure the quality or safety of drugs.

Fifty five per cent of Dutch men say they receive Viagra spam. Of those, 85 per cent say they are annoyed by it. About 46 per cent of people that receive Viagra spam think that Pfizer sends out these solicitations, a spokesman for the firm says. "We get a lot of phone calls from people asking us why we do this."

Earlier this year Pfizer, along with Microsoft, filed 17 parallel lawsuits against two "international pharmacy spam rings" selling what they claim were generic versions of Viagra online. Pfizer said it would also take action to ban the domain names of a dozen other websites, which sport addresses like freegenericviagra.com.®