Most cases of cancer are down to unhealthy lives, rather than bad genes, doctors said last night.

They said that factors in the world around us, from diet, to sunlight, cigarettes and disease, play a far bigger role in fuelling cancer than dodgy DNA.

Up 90 per cent of cancer cases would be wiped up if all these triggers could be avoided.

Dr Emma Smith, of Cancer Research UK, said: 'Healthy habits like not smoking, keeping a healthy weight, eating a healthy diet and cutting back on alcohol are not a guarantee against cancer, they do dramatically reduce the risk of developing the disease.'

While the advice may not seem surprising, scientists are divided about how much cancer is caused by what we do and how much is unavoidable.

The controversy was stoked a year ago by research that claimed that most cases are caused by errors in DNA that are generated at random as the body ages and its cells divide.

The researchers said this meant that most cases of cancer were down to 'bad luck', rather than an unhealthy lifestyle.