One of Britain's top surgeons is considering taking legal action over the "rationing" of life saving obesity surgery on the NHS.

Professor John Baxter, president of the British Obesity Surgery Society said that the health service was putting patients lives at risk by not funding the surgery for many.

He accused Primary Care Trusts (PCT’s) of limiting the number of operations they performed because of the cost, which can be up to £6,000.

According to professor Baxter the operations, which include gastric band surgery, would pay for themselves within four years, because they would reduce the number of obesity-related conditions, such as diabetes.

The health service currently carries out fewer than 300 stomach-shrinking operations a year.

Professor Baxter said that half of all PCTs in England were ignoring guidelines that morbidly obese patients should have the surgery, which can lead to rapid weight loss.

Professor Baxter pointed to other patient groups, which used legal action to advance their case for expensive treatments.

These include breast cancer patients who went to court in a battle over the non-availability of the drug, Herceptin, which was eventually allowed for the early stages of the disease.

Obesity costs the NHS an estimated £1 billion a year, because of the expense of dealing with related conditions including heart disease and even some forms of cancer.

An estimated 1.2 million people in Britain are now so heavily overweight that they qualify for obesity surgery.

At the current rate at which the NHS performs the operations it would take the health service 54 years to clear the backlog.

Significant amounts of weight and may be lost and  life expectancy increased by those who undergo the surgery, studies have shown.

Last month Alan Johnson, the Health Secretary, warned that today's obese children faced dying 11 years younger than their slim classmates.

The National Institute for Health and Clinical Excellence (NICE) says that patients are eligible for the surgery if they have a BMI more than 40, and previous attempts at diet or prescriptions of weight-loss drugs have failed.

Anyone with a BMI between 35 and 40 can also be eligible, if they have an obesity-related condition such as diabetes.

But some PCT’s require a BMI of more than 50 before they will consider the operation.