The ASA says many firms are trying to jump on the Viagra bandwagon by advertising impotence 'cures' with names which are suspiciously like Viagra.

One, for a herbal treatment called Vigorex, actually uses the words: "Finally available in the UK. The potency pill that swept America".

It says the pill will give men "sexual powers beyond their wildest dreams" and should be snapped up before the "sheer frenzy" which will occur when it is officially launched in the UK.

The ASA is investigating Vigorex on the basis that it is trying to pass off as Viagra, the pill which is claimed to 'cure' impotency and give middle aged men the libido of a 20-year-old.

Herbal remedies

Viagra, manufactured by US company Pfizer, is expected to get the go-ahead for European sales this month, despite reports of over 100 deaths worldwide linked to it.

The drug acts by narrowing the blood vessels supplying the penis, causing an erection.

Most of the fake Viagra drugs are herbal remedies, containing Yohimbe bark, described as a natural aphrodisiac.

Many are marketed on the Internet, although some are also being advertised in magazines and newspapers.

Vigorex has its own Website where it is described as a strawberry-flavoured erection lotion.

Injunction

Other herbal remedies with names similar to Viagra include Vaegra, a vitamin and herbal supplement, and Viagro, another herbal remedy.

Legal action was taken against both. The US Federal Trade Commission won a temporary ban on Vaegra last month.

Some herbal remedies charge as much as the real Viagra. Experts claim they have not been subjected to any rigorous testing and claims about their effectiveness are dubious.

A UK television documentary revealed that the UK Counterfeit Intelligence Service is investigating several impotence 'cures', some of which use some of Viagra's ingredients.

Many are reportedly being manufactured in Thailand and India.

Other herbal cures, advertising themselves on the internet as "natural alternatives" to Viagra include Milagro, also made from Yohimbe bark, and Biogra.