The gene was discovered by chance

The gene, called E2F3, produces a protein which helps the disease to spread.

The Institute of Cancer Research hopes the discovery could lead to new treatments to treat the disease, which kills 5,000 Britons each year.

"E2F3 is the missing link in our knowledge of this disease," said lead scientist Professor Colin Cooper.

The institute's team were actually researching genes linked to prostate cancer when they stumbled upon E2F3.

Multiple copies

They found that there were multiple copies of this gene in cancer cells in the bladder.

They also discovered that there was a direct link between the amount of E2F3 in each cell and the stage of the cancer.

This is a very exciting development Professor Colin Cooper

The scientists hope the findings will lead to a new drug to block this protein and fight cancer in the bladder.

"This is a very exciting development," said Professor Cooper.

"These findings will boost the development of new treatments to target bladder cancer as well as predicting the aggressiveness of a particular cancer, leading to tailor-made, more effective treatments for each individual patient."

The scientists also believe the gene may be implicated in other cancers.

"We await other findings that will arise from this discovery with anticipation," said Professor Peter Rigby, chief executive of the Institute of Cancer Research.

The study was funded by Cancer Research UK, the Department of Health and the Medical Research Council.