The number of people diagnosed with kidney cancer each year is at a record high - partly fuelled by obesity, figures show.

Kidney cancer cases hit more than 9,000 in 2009, treble the figure of just under 3,000 in 1975.

It is now the eight most common cancer in Britain, climbing from 14th place in 1975.

Experts believe that, after smoking, obesity is the most preventable risk factor for developing the disease, increasing the risk by 70%.

Cancer Research UK, which released the figures, estimates that about a quarter of kidney cancer cases in men and 22% in women are linked to being overweight.

Overweight people produce higher levels of some hormones which can help fuel cancer.

In 2009, almost a quarter of adults in England were obese. A further 44% of men and 33% of women were overweight.

Professor Tim Eisen, a Cancer Research UK kidney cancer expert based at the University of Cambridge, said new drugs had been developed to destroy the blood supply to the kidney tumours, but were not a cure.

"It is best to prevent the problem in the first place - maintaining a healthy weight and not smoking are the best ways of doing that.

"The other important point is to see your doctor if you have noticed blood in your urine as this can be an early sign of something wrong.

"If the kidney cancer is caught early, it can often be cured by surgery."

While some of the increase in cases could be down to better detection of kidney tumours, evidence suggests there has also been a rise in the number of advanced kidney cancer cases - suggesting other factors are also in play.

In 1975, 2,953 people were diagnosed with kidney cancer in Britain.

Latest figures show there were 9,042 cases in 2009, up from 8,848 in 2008.

Newsreader Nicholas Owen, who is a kidney cancer survivor, said: "It's worrying to see the number of cases rise. But it is so important for people to go to their doctor if they experience any symptoms like blood in urine.

"The chances are it won't be cancer, but if it is, spotting it early means that treatment is often easier and many more people survive."

Sara Hiom, director of information at Cancer Research UK, said: "Obesity is not only linked to kidney cancer but six other types of cancer and other diseases as well.

"Kidney cancer survival rates have greatly improved over the last 35 years thanks to research funded by our generous supporters.

"To ensure we continue to make progress, it's really important that the disease is diagnosed as early as possible to give patients the best treatment options."