The number of women being screened for breast cancer is worryingly low in many areas, campaigners say.
A minority said they would rather not know if they had breast cancer
The National Breast Screening Programme aims to screen 70% of women.
But Breakthrough Breast Cancer and the All Party Parliamentary Group on Breast Cancer says it is up to 20% lower in many places.
An ICM poll of 2,500 women found one in six who missed their mammogram did so because it was at an inconvenient time, and that they did not make another.
In one part of London the take-up rate for screening is only 51% - 19% below the target rate.
Campaigners said screening should be made more accessible and the importance of being checked should be stressed.
The campaigners also called for an investigation into why there are disparities in the uptake of screening invitations across the UK.
The survey also found women did not have a realistic picture of the benefits of breast screening or their ability to spot signs of the disease.
Of those who reported not attending their breast screening appointments:
- 7% thought they were not in a high-risk category for developing the disease - even though over 80% of all breast cancers occur in women aged 50 and over and the risk of developing the disease increases with age,
- 9% felt they knew their own bodies well enough to spot breast cancer - even though half of breast cancers detected by screening are too small to be felt by the human hand,
- One in 10 said they would rather not know whether if had breast cancer - even though early diagnosis and treatment increases the chances of survival
The All-Party Parliamentary Group and Breakthrough are calling on the Health Secretary John Reid to make screening services appointments more flexible so women can access them outside working hours, or by screening women in units near to their work instead of their homes.
They are also calling for a renewed publicity campaign about the importance of breast screening appointments and the common signs and symptoms of cancer
Anne Campbell MP, secretary of the All-Party Parliamentary Group on breast cancer said: "We already know from NHS Screening Programme's own statistics that some parts of London and other areas with highly mobile populations, socio-economic deprivation and a significant minority ethnic population, the uptake of screening invitations fall as much as 20% short of the programme's 70% uptake target.
"While we can make educated guesses about why this might be, more work needs to be done to find out what the reality is, and how we can make sure that breast screening services are as accessible as possible to all women."
Antonia Bunnin, policy & campaigns director at Breakthrough Breast Cancer told BBC News: "We think many women might not be able to attend appointments during working hours.
"There would be benefits in increasing the flexibility and availability of screening."
She added: "Research from the National Audit Office found women from lower socio-economic and ethnic groups are less likely to attend screening appointments.
"It's important these groups are targeted, and information for them is improved."
Richard Winder, deputy director of the NHS Cancer Screening Programmes said more women were having mammograms than ever before, with over 80,000 additional women attending last year.
He said women who did not attend were offered an alternative appointment.
Mr Winder added: "We are committed to continuing to improve the accessibility of the programme and to investigating variances in the acceptance of screening invitations.
"To this end we have a number of initiatives underway, including a major research project looking at how best to communicate with hard-to-reach communities such as minority ethnic and deprived groups.
"This will provide a better understanding of barriers that prevent women from attending for screening and how they can be overcome."