UK scientists have identified a gene they say increases the risk of bowel cancer by 20%.
Around 35,000 bowel cancer cases are diagnosed every year in the UK
Researchers from London and Edinburgh pinpointed the gene after scanning the DNA of over 30,000 people - half of whom had the disease.
Writing in Nature Genetics, they estimate that half the population carry the genetic fault which is associated with one in 10 bowel cancers.
However, the increased risk is too small to warrant a genetic test.
In the future, as more genes associated with the condition are identified, it may be possible to design a test for a combination of genes to identify those most at risk, improving prevention and diagnosis, the researchers said.
Several genes are already known to contribute to bowel cancer risk but are extremely rare among the population accounting for less than 5% of bowel cancer cases every year.
But it has been estimated that genetic risk contributes to around a third of cases.
Professor Malcolm Dunlop, from the University of Edinburgh and the Medical Research Council's Human Genetics Unit, compared the DNA of around 8,000 bowel cancer patients from North America, France and Scotland, to that of around 8,000 healthy people.
By doing a "whole genome search" the team tracked down the gene which is faulty more often amongst bowel cancer patients than in people without the disease.
A second study carried out by researchers at The Institute of Cancer Research and Cancer Research UK's London Research Institute identified the same faulty gene after analysing the DNA of a similar number of patients and healthy people from England.
Scientists recently found that men who have the same genetic variant are at an increased risk of developing prostate cancer.
Professor Dunlop said: "We are now using an even more refined genome-wide scan to discover yet more genes linked to bowel cancer risk.
"By identifying these genetic variants, we will be in a better position to understand how such changes can lead to cancer."
Professor Ian Tomlinson, who led the second study said: "This is an important first step but we still have a long way to go before we have a complete picture of all the genes that are involved in inherited bowel cancer risk.
"Eventually it may be possible for scientists to design treatments to prevent people at increased risk of the disease from developing bowel cancer altogether."
Cancer Research UK is launching similar genome wide studies for lung and ovarian cancer and scientists hope to find out more about the genes linked to these cancers as a result.
Harpal Kumar, chief executive of Cancer Research UK who are funding further gene studies in ovarian and lung cancer, said: "In the future we hope studies like this across a range of cancers will help people at increased risk of the developing the disease through the development of tailored screening and treatment programmes."
Dr Rob Glynne-Jones, chief medical advisor at Bowel Cancer UK and consultant clinical oncologist at Mount Vernon Hospital said: "This discovery of a common bowel cancer gene is further proof that we are really getting to grips with what causes bowel cancer.
"Patients will be very excited to know that this research helps us to identify why at least 10% of people are at risk from the disease."