Women should be given more information about the potential risks of being screened for breast cancer, say doctors.
Thousands of women are screened for breast cancer each year
A controversial article in this week's British Medical Journal suggests women are not being told that screening has "benefits and harms".
Researchers from the University of Leicester said women should be warned of the psychological and emotional impact of the scans.
They suggested that women should also be told that the chances of cancer being picked up are low and that it may increase their chances of having unnecessary surgery.
The researchers quoted a recent study which found that 1,224 women between the ages of 40 and 74 would have to be screened for 14 years to prevent one death from the disease.
They also highlighted figures which suggest that one in five of the cancers detected as a result of screening are ductal carcinomas in situ - cells inside the milk ducts which are beginning to turn cancerous.
Most of these will turn out to be harmless. Only 40% of cases will require removal of a breast.
However, women are faced with a difficult choice - whether to have surgery or to wait to see how the cancer develops.
The researchers said providing women with the full facts would allow them to make informed decisions.
"The public receives highly conflicting messages about the effect of screening," they said.
"Harms are often dismissed as a price worth paying for the perceived general good.
"Individual women may suffer physical, emotional, social, financial, intergenerational or psychological harm," they said.
"It is important, therefore, that women are able to understand the potential harms and can make an informed choice for which they are prepared to take responsibility."
They added: "The information inviting women to screening must be improved. It is unacceptable that women taking tests continue to suffer morbidity and regret because they found out the harms of screening from experience."
Breast screening was introduced gradually in the UK between 1978 and 1997.
All women between the ages of 50 and 64 are now invited to have a breast X-ray every three years.
There programme will be extended to all women up to the age of 70 by the end of 2004.
A study by Cancer Research UK, published in April, suggested that screening programmes are effective.
It found that screening can cut the number of deaths from breast cancer by half and recommended that the NHS programme is extended to women aged 40 and above.
Figures published last month show that more than 40,000 women are now told they have the disease each year.
But more women are now surviving the disease - three out of four live five years or more after diagnosis.
According to the NHS breast cancer screening programme, scans save 1,250 lives each year.
It sends a leaflet explaining screening to all women who are invited for scans.
It explains how screening works and also tells women that while scans are the best way of detecting cancers they are "not perfect".
A spokeswoman said: "The leaflet provides women with balanced information on screening."
Anna Wood, policy analyst at Breast Cancer Care, said: "We support the screening programme and we support any research that looks into the information that women are currently getting."