A survey of almost 1,000 women found that nearly half were unable to identify any of the correct risk factors. Age is the main risk but only one in 20 women knew that the disease increased with age and was commonest in those over 60.
Some specialists have argued that the proliferation of breast-cancer charities and the high public profile they have achieved in recent years has increased anxiety among women without increasing knowledge. The use of models and personalities, such as the former Spice girl Geri Halliwell, has also created the false impression that breast cancer is a disease of younger women.
The survey, published today by the Imperial Cancer Research Fund (ICRF), found that levels of anxiety were highest, and pessimism about the likelihood of surviving breast cancer greatest, among women whose knowledge of the disease was poorest.
The highest levels of anxiety were among the young who are at lowest risk. More than 80 per cent of those aged 16 to 24 said the thought of breast cancer scared them. Older women were less worried despite being at higher risk. The lifetime risk is quoted as one in eleven but this applies to women up to the age of 85. For the under-thirties the risk is one in 2,165.
Professor Jane Wardle, head of the ICRF's health behaviour unit, said: "It is definitely an issue we need to consider - whether the implicit messages coming with breast-cancer publicity are always accurate. The implicit message of using a Geri Halliwell front person is, `This is the sort of person at risk'." She added: "What became clear from the survey was that people had very poor awareness of the risk factors."
Even among the oldest women, breast cancer never causes more than one in five of all deaths. Six times more women die of heart disease (75,000 a year) than breast cancer (13,000 a year) but the former is feared less.
A spokeswoman for the ICRF said: "The women most at risk are those aged 50 and above and if we can increase awareness among them and get them to go to their GPs earlier it increases the chance that any treatment given will be successful."
About 30,000 women a year in Britain are diagnosed with breast cancer and one-third wait longer than three months for treatment, partly because they postpone going to a GP and partly because of the wait between referral and a hospital appointment. In a study published earlier this year in The Lancet, Professor Michael Richards, of St Thomas' Hospital in London, and colleagues concluded that if the total delay could be reduced to less than three months for all women, at least 500 lives could be saved.
n Age - commonest in older women
n Family history - if two or more close relatives affected, one before age 55.
n Early onset of periods
n Late menopause
n Late childbearing
n Alcohol consumption