Research has found that people from poorer backgrounds are less likely to detect bowel cancer at an early stage, because many are failing to use home testing kits sent to them.
Diagnosing bowel cancer at an early stage can increase survival rates by 15 times, but Cancer Research UK found there was a divide in the people using testing kits.
More than 40,000 kits were sent out to people aged between 60 and 74 in London. They were returned by 49% of people in the most affluent areas, but only 32% of those in the poorest parts used the kits.
Professor Jane Wardle, lead author of the research, said: "There's a real danger that bowel cancer could increasingly become a disease of lower social class if these figures hold true across the UK.
"We know that more than 90% of bowel cancer patients survive if the disease is caught at the earliest stage, compared with around 6% for cases detected at the latest stage.
"Screening helps to spot early signs of bowel cancer, as well as pre-cancerous growths that don't cause any symptoms, so it's important that everyone who receives a testing kit takes part."
Professor Wardle added that research was needed to find out why people were reluctant to use the detection kits.