Just 22% of people manage to eat the recommended "five a day" portions of fruit and vegetables, research suggests.
Only 17% of people in low income households eat the suggested amount compared to 27% in higher income groups, the poll conducted by World Cancer Research Fund (WCRF) has found.
Consumption varied slightly around the country with 18% of people in the north of England meeting the quota, compared to 26% in the south, the survey of 2,128 adults 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 to incorporating plant foods into our daily diets."
A spokeswoman for the charity said it commissioned the survey to coincide with Cancer Prevention Week, which starts today.
A Department of Health spokesman said: "We know we need to do more to encourage people to eat their five a day and help prevent diseases like cancer.
"That is why, through our Change4Life campaign, we invested around £10 million last year on encouraging healthier lifestyles.
"This included things like the Supermeals campaign which promoted five a day by giving recipe ideas and money-off fruit and vegetables in retail stores.
"We are also encouraging children to get their five a day through the scheme which gives them a free piece of fruit or vegetable at school every day. Over 2.1 million children benefit from the scheme."