Nearly a quarter of cancer diagnoses in England are made when patients arrive at hospital in an emergency, a study has found.
Research by the National Cancer Intelligence Network (NCIN) found that 23% of cancer cases are detected only as patients undergo emergency treatment.
The figures are even starker for sufferers of acute leukaemia and brain cancer, where well over half of cases are discovered at a critical stage.
Pensioners and those under 25 are most likely to be diagnosed with cancer during emergency procedures, while poor people are more likely to suffer from late detection than the rich.
The study found that people whose cancer was detected at an emergency stage were significantly more likely to be die within a year than those whose illness was discovered earlier.
Harpal Kumar, the chief executive of Cancer Research UK, said: "The figure for diagnoses via emergency presentations is way too high. This statistic helps explain why we have lower survival rates than we would hope to have, lower than the best countries in Europe."
He told the Daily Telegraph: "We need screening programmes to be rolled out as early as possible and GPs given rapid access to the tests that will enable patients to be moved quickly through the system."
Sara Hiom, director of health information at Cancer Research UK said the number of patients whose cancer is only being discovered at an emergency stage is "alarmingly high".
"We hope the Government will seriously consider the best way to tackle this problem in their revised cancer strategy, which is due in the coming months," she said.
A spokesman for the Department of Health said: "We are committed to improving cancer outcomes. Earlier diagnosis is crucial to match the best survival rates in Europe."