The survey by the Cancer Research Campaign found that many women worry that have inherited a risk of developing the disease.

A third of the women studied still over-estimated their chances of developing breast cancer even after the risks were explained to them by genetic experts.

The study, published in the British Journal of Cancer, looked at 282 women in London with a family history of breast cancer.

The women were at various levels of risk of developing the disease because of their family history.

A major aim of the study was to discover whether the women's worries were reduced once they had their actual risk explained to them.

It found that a third of them continued to over-estimate their risk of getting breast cancer a year after consulting a genetic expert.

The belief they had about their risk had not changed.

Lead researcher Dr Maggie Watson said: "Our research shows that women worry a lot when they think they are at risk regardless of whether the genetic experts considered them to be or not.

"We want women, who may be at risk from their family history, to understand more what that risk is."

Dr Watson said more work was needed to ensure women had a more realistic attitude towards breast cancer, and that their fears were allayed.

In some families, where several members have devleoped the same cancer, there may be an increased risk because of an inherited faulty gene.

But these faulty genes account for only a minority of all breast cancers, approximately five to ten per cent.

Lifetime risk

Professor Gordon McVie: "We must reassure women"

The women who took part in the study were given their specific lifetime risk by genetic doctors.

Lifetime risk is based on living until 75, and is expressed as a ratio, for instance one in 12..

Two-thirds of the women could not remember the figure after the consultation.

When the women were told about their lifetime risk in more general terms, whether it was high or low, a third of them continued to over-estimate that as well.

Researchers also found that before consultations 28% of the women worried excessivley about getting breast cancer.

A year later the number remained high, with 23% saying their worries had not been reduced.

Cancer Research Campaign director general Professor Gordon McVie said: "If women are not convinced about the level of risk they are at from getting breast cancer, even after meeting a genetic expert, they will continue to be needlessly worried and distressed.

"They are also likely to go on seeking unnecessary screening.