More than a million prescriptions for antiobesity drugs are now given out to patients each year, more than eight times the number dispensed nine years ago.

Two drugs, orlistat (Xenical) and sibutramine (Reductil), made up the bulk of recent prescriptions issued by GPs in England, the NHS Information Centre said. Sibutramine works by altering chemical messages to the brain that control feelings about food, and orlistat prevents some fat absorption.

The drugs are used when attempts to lose weight through diet and exercise alone have failed, and should be combined with other efforts to lose weight. Nearly a quarter of adults are obese, a figure up 50 per cent in the past ten years, while one in six children aged 2 to 15 is classed as obese, up from one in ten.

The net ingredient cost (NIC) of the drugs increased from £4.9 million in 1999 to £47.5 million in 2006; and the NIC per item rose from £38 to £45.

Opposition parties said the figures showed that the Government was losing the battle against the rising tide of obesity.

The NHS also said that more than one in five men and nearly one in four women are now at very high risk of developing health problems, based on waist circumference and BMI, or body mass index. The report comes a week after the Government launched a £372 million strategy aimed at cutting levels of obesity in England.

The increasing use of obesity drugs is partly accounted for by the fact that more have come on to the market. Orlistat was licensed in Britain in 1998 and sibutramine in 2001.

Jim Kennedy, prescribing spokesman for the Royal College of GPs, said that the condition was also now being taken more seriously. He said: “Government, patients and doctors are all more aware of the risks and therefore more willing to discuss obesity. This means there is more of a willingness to consider treatment options.”

He said that patients should only be prescribed obesity drugs alongside a programme to encourage a healthier lifestyle by altering diet and increasing physical activity. He added that the one million prescriptions a year should be seen in the context of 13 million GP consultations each week.

But the National Obesity Forum described the increase in the use of obesity drugs as horrific.

Alan Maryon-Davis, president of the Faculty of Public Health, said: “Doctors and other health professionals do not have the time to spend on the in-depth diet and exercise advice that is really needed. My fear is that these drugs of last resort are actually used quite early on. It is too easy to turn to the prescription pad.”

The report, released yesterday, also included the findings of a survey that questioned more than 21,000 adults and children about their food consumption and activity levels.

Less than a third of adults and a fifth of children were found to be eating the recommended five daily portions of fruit and vegetables. Fewer than three out of ten women and only four out of ten men took part in at least 30 minutes of activity at least five days a week, though this was up from two out of ten women and three out of ten men in 1997.

Andrew Lansley, the Shadow Health Secretary, said: “Drug treatments are a short-term solution from a government that can’t see beyond the short term. The burden obesity is placing on our already overstretched NHS is becoming more and more unmanageable.”

Dawn Primarolo, the Minister for Public Health, reiterated that doctors should not prescribe drugs for obesity unless they were clinically necessary.

Lord Winston, the fertility specialist, said yesterday that obesity was the cause of an increasing level of infertility. He said that, in a number of cases, couples struggling to conceive may simply need to lose weight. “There is unquestionable evidence that some people who are overweight are much more likely to be infertile,” he said. “For people who are infertile, weight loss is one of the biggest things you can do.”

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