Just 22pc of people manage to eat the recommended "five a day" portions of fruit and vegetables, research suggests.
Only 17pc of people in low- income households eat the suggested amount compared to 27pc in higher-income groups, the poll conducted by World Cancer Research Fund (WCRF) has found.
The figures show that many are still finding it difficult to eat healthily, a spokeswoman for the charity said.
WCRF head of education Kate Mendoza said: "Getting at least five portions of fruit and vegetables a day is the building block of a healthy diet.
"A diet based on plant foods, such as whole grains and pulses as well as fruit and vegetables, can reduce cancer risk as research shows they protect against a range of cancers. Recent research has confirmed that foods containing fibre reduce the risk of bowel cancer.
"A lot of WCRF's work focuses on raising awareness of the importance of diet, physical activity and body weight in relation to cancer risk. Although people are more aware of the significance of eating 'five a day' than they used to be, it is clear that there are still barriers."