The BBC's Richard Hannaford reports on the side effects

Campaigners say they have been contacted by thousands of women who say the treatment has made them ill.

Complaints include "banging" headaches, hair loss, loss of balance and abscesses in the mouth.

HRT is used to treat various conditions women may experience during the menopause.

Divided opinion

Opinion is divided over the value of HRT. Recent research shows the therapy could help prevent brittle bones when taken in combination with the hormone progestin.

Other research shows that the longer women take HRT, the more likely they are to develop other diseases such as breast cancer.

However, for brittle bones - or osteoporosis - there are new drugs that may be more effective than HRT.

Maggie Tuttle: Runs a helpline

One campaigner is Maggie Tuttle. She runs a helpline for HRT users from her home and received the therapy for 15 years.

She said she started to suffer side effects soon after starting the treatment.

She said: "Within a very short period of time I had this sort of banging, banging, banging in my head. It just wouldn't go away, it was so severe."

She is now helping to promote a conference about the problems of HRT and the benefits of alternatives.

About three million women in the UK receive HRT. It is administered through either patches or pills.

Unlikely connection

However Dr Malcolm Whitehead, a consultant gynaecologist, doubted that HRT is responsible for the side effects described.

He said: "I see women, perhaps two a month, who come to me complaining of hair loss who have never taken HRT.

"Indeed, they are asking me to give them HRT to try to make their hair better."

He added: "I do not know of any evidence that estrogens impair the ability to walk, otherwise girls going through puberty would suddenly start falling sideways."