A leading osteoporosis researcher has resigned from the Government's medicines watchdog after a disagreement over the use of hormone replacement therapy.

Professor David Purdie, from the Edinburgh Osteoporosis Centre, said he did not agree with the Committee on the Safety of Medicines (CSM) that HRT should no longer be the first choice treatment to prevent the bone disease.

The advice from the Medicines and Healthcare Products Regulatory Agency (MHRA) followed a Europe-wide review of the risks and benefits of the therapy, most commonly used to relieve the symptoms of the menopause.

Professor Purdie said: "I have offered my resignation to the CSM. I believe that GPs should retain the option to use HRT in women in their early fifties to prevent osteoporosis. I think HRT is effective, reliable and safe in preventing osteoporosis. I believe woman can use HRT when they are younger and then move on to non-hormonal treatments."

Yesterday's advice followed international research on the dangers of HRT, including the Million Women Study in August, which said the therapy was linked to breast cancer.

Professor Purdie said he believed the committee had rushed forward in issuing the advice without allowing for the research to be reviewed.

The Department of Health said it was aware of Professor Purdie's resignation offer. A spokeswoman said: "He should have made his concerns known to the committee before the advice was submitted. We stand by the advice that HRT can be used in the short-term treatment of post-menopausal symptoms but should no longer be the first choice for the prevention of osteoporosis."

The MHRA's new advice said HRT was beneficial for the treatment of menopausal symptoms, but the minimum dose should be used for the shortest time. The agency said HRT should not be the first choice of therapy for preventing osteoporosis.

Professor Gordon Duff, the chairman of the CSM, said yesterday that the new advice did not mean there needed to be any urgent change in treatment, but that women receiving HRT as a preventive measure should have their treatment reviewed at their next routine appointment.

As well as breast cancer, HRT has also been linked with an increased risk of endometrial and ovarian cancers and heart attacks.