There are eight unexplained symptoms most closely linked to cancer, and they have been identified by researchers.

The team from Keele University also points to the age at which patients should be concerned by the symptoms, which include blood in urine and anaemia.

Other symptoms include rectal blood, coughing up blood, breast lumps or mass, difficulty swallowing, post-menopausal bleeding and abnormal prostate tests.

Cancer Research UK said that unusual changes in a person's health should be checked.

The researchers have been looking for symptoms that gave a one in 20 or higher chance of turning into cancer.

Although it is still a relatively low chance of anyone with the symptom having the disease, any suspicion of cancer could mean the patient is sent for tests more quickly, in order to catch the disease as early as possible.

The figures for each symptom was calculated by combining the results of 25 previous studies.

They found that if the patient is younger than 55, only two signs reached the 'one-in-20' threshold.

These were a prostate examination that gave unusual results, and a breast lump.

After 55, only in males, there was evidence that difficulty swallowing could be a sign of esophageal cancerm while blood in urine was highlighted as a concern for men and women over age 60.

Dr Mark Shapley, who was leading the research, said "GPs should audit their management and reflect upon these cases as part of their appraisal to improve quality of care.

"There should be more open public debate on the level of risk that triggers a recommendation for referral by a GP."

Professor Amanda Howe, honorary secretary of the Royal College of General Practitioners said, "It's useful to see these well-known 'red flag' symptoms and signs validated in primary care research, and reinforces the importance of encouraging patients to discuss worrying symptoms early with their GP."

A spokesman for Cancer Research UK said that these were by no means the only potential cancer warning signs.

"The particular symptoms this study has highlighted are already thought of as important potential signs of cancer, but there are more than 200 different types of cancer, which cause many different symptoms.

"So if you notice an unusual or persistent change in your body it's important to get it checked out. When cancer is diagnosed at an early stage, treatment is often more likely to be successful."