Women in Scotland could be used like human guinea pigs in a massive hormone experiment if a controversial new sex drug - touted as 'pink Viagra' - is made available on prescription.

Doctors in America and the UK have told The Observer they have serious concerns about the risks of cardiovascular disease and breast cancer associated with Intrinsa, a testosterone patch developed by the pharmaceutical company Procter & Gamble.

They claim company-funded trials, which have not been published in peer-reviewed journals, are inadequate to assess the drug's long-term safety.

Intrinsa works by slowly leaking testosterone into the body, through a patch placed on the stomach, to help stimulate women's sex drive. Procter & Gamble claims the patch can increase sexual activity by 74 per cent.

However, critics point out that the drug was tested for only six months on a sample of 1,095 women whose ovaries had been removed and who were also taking oestrogen.

With some industry reports suggesting that P&G is planning a global marketing campaign, there are concerns that Intrinsa will be promoted as a lifestyle drug. At the end of last year a panel of advisers to the US Food and Drug Administration unanimously rejected the patch as a treatment for women with 'hypoactive sexual desire disorder'. Although the panel said the patch benefits were 'clinically meaningful', they ruled that the trials were inadequate.

However, it is understood P&G has since applied to get the drug licensed in Europe. If passed, the patch could be available through the NHS in Scotland and the rest of the UK within two years.

Dr Steve Nissen, a cardiovascular expert and adviser on the FDA panel, said the patch's potential to increase heart attack risk was substantial, based on the company's trials: 'I don't want to expose several million American women to the risk of myocardial infarction and stroke in order that they can have one more sexual episode a month.'

Mark Chakravarty, a spokesman for P&G, said trials had indicated no serious health concerns and dismissed the suggestion that the company had created HSDD. 'Female sexual dysfunction is recognised by the medical and psychiatric community as a disorder. Suggesting that this condition is created does not help sufferers,' he said.