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Scientists have discovered what could be the first step towards a DNA test to detect the early signs of bowel cancer.

Tests on two distinct genes were highly accurate in distinguishing between tumours and benign polyps - growths in the bowel that can become cancerous.

While not all polyps in the bowel become cancerous it is thought almost all bowel cancers develop from polyps.

The Cambridge study, in the BMJ journal , analysed 261 samples from patients with benign polyps or bowel cancer.

In particular it looked at what are called DNA methylation patterns - a key process in cell development.

The researchers at Cancer UK's Cambridge Research Institute at Cambridge University say that DNA methylation is essential for life.

In healthy cells a compound called a methyl group is tagged to DNA where it acts as a "red light", preventing certain genes from producing proteins.

But this process can go wrong in cancer cells and DNA methylation can also contribute to the cause and development of cancer by blocking important "protective genes"

Dr Ashraf Ibrahim, the lead author of the study, says studying molecular changes could make diagnosing bowel cancer much simpler in the future.

"The molecular signals, which tell genes whether to make proteins or not, can become jumbled in cancer cells. We've identified several places where this signal becomes damaged and shown this is linked to bowel cancer development.

"The majority of bowel cancers develop from benign polyps that turn cancerous - and this crucial research deepens our understanding of the molecular changes behind this development.

"This first step in detecting molecular 'flags' for bowel cancer, could, one day, lead to a simple test to search DNA for the early signs of the disease."

Dr Lesley Walker, Cancer Research UK's director of cancer information, says the research opens up the possibility of much earlier diagnosis of bowel cancer, when it is easier to treat.

"We've come a long way in improving screening and developing better treatments - our scientists have been involved in testing many drugs that are used to treat bowel cancer and they've had a key role in pinning down the genetic causes of the disease.

"But there is still more to be done. Research like this is vital in our goal to develop the best methods to detect, monitor and treat cancer and improve survival."

More than 38,000 people in the UK are diagnosed with the disease each year.