At least one in five women have not checked for signs of breast cancer in the last year, a YouGov poll suggests.
The survey of 1,004 women and 729 men found that 76% of women aged 18 and over had ever checked for signs of breast cancer, including 41% who had done so in the last month.
Some 18% said they had checked themselves in the last six months but 11% of women overall had never checked their breasts.
Among the men, 80% were aware they could develop breast cancer themselves, though only one in five has ever done a breast exam.
Overall, most men (69%) have never performed a check for signs of breast cancer.
Every year, around 11,500 women and 85 men die from breast cancer in the UK.
The new poll, shared with the PA news agency, also found that nearly two-thirds of Britons (63%) have been affected by breast cancer either directly or through a loved one.
A quarter (27%) of people have a family member who has had breast cancer, 22% have had a friend diagnosed and 2% have had it themselves.
A further 33% knew somebody else with breast cancer.
Meanwhile, women were more likely to know or have known someone with the illness (72%), compared to men (53%).