More than one in four women invited to breast cancer screening do not attend, NHS figures have shown.
Some 2.2 million women were invited for the screening in 2008 but 1.7 million attended. Experts have predicted that full attendance could have saved 600 lives in England.
In January this year, the number fell further as less than 70% of all women invited attended their screening appointments.
More than 45,000 new cases of breast cancer are diagnosed every year, making it the most common cancer in the UK. The illness is responsible for 12,000 deaths every year.
In all parts of the UK, women aged 50 to 70 are invited for screening, except in Northern Ireland, where women are screened from age 50 to 64.
All women aged 47 to 73 will be invited for screening in England in the next 12 months or so as part of an extension programme.
Results from the NHS breast screening programme in England show that around 10,000 cases of breast cancer are diagnosed this way each year, saving around 1,400 lives annually.
Professor Julietta Patnick, director of the NHS Breast Cancer Screening Programme, said: ‘The programme is working hard to understand the factors that affect women’s uptake of invitations in order to provide the best possible service, and to provide women with the right information for them to make their decision.’