A weight-loss drug banned in the U.S. over fears it can heighten the risk of suicide has been given the go-ahead in Britain.

Acomplia will be available to overweight or obese patients who cannot take, or who have had no success with, the two other weight-loss drugs available on the Health Service.

But a series of scientific studies have raised concerns that it can induce suicidal thoughts in those already suffering from depression.

Acomplia will be made available to overweight or obese patients who cannot take, or who have had no success with, the two other weight-loss drugs available

The drug, taken orally as a pill once a day, has not been authorised in the U.S. because of safety fears, although it is available in France and Germany.

Acomplia, also known as rimonabant, went on sale in Britain in June 2006 but approval from the National Institute for Health and Clinical Excellence, or Nice, for use on the NHS was issued only yesterday.

Trials have shown that it could help two out of five patients lose 10 per cent of their weight.

In July last year, the European Medicines Agency warned that rimonabant may be unsafe for patients suffering major depression or who were taking antidepressants.

Evidence suggested one in ten of those taking the drug may develop mental side-effects including low mood and depression, anxiety, irritability, nervousness and sleep disorders.

The Nice guidance recommends rimonabant 'as an addition to diet and exercise for adults who are obese or overweight and who have had an inadequate response to, or are intolerant of' the other two main weight-loss drugs.

These are Xenical, also known as orlistat, and Reductil, or sibutramine.

However, Xenical cannot be used by those with bowel problems, and Reductil cannot be used by those with high blood pressure.

The go-ahead means doctors will have a choice of more drugs to help those wanting to lose weight. All the drugs cost about £2 a day.

Nice's guidance said treatment with Acomplia should be continued beyond six months only if the person has lost at least 5 per cent of their initial body weight since starting on the drug.

Obesity crisis: Britain is becoming the fattest nation in Europe, a recent study found

Patients should be taken off the drug if they return to their pre-treatment weight.

The guidance added: 'Treatment should not be continued for longer than two years without a formal clinical assessment and discussion of the individual risks and benefits with the person receiving treatment.'

Andrew Dillon, chief executive of Nice, said: 'This is good news for patients for whom orlistat and sibutramine are not effective.

'Being overweight or obese can lead to a range of serious health problems, including heart disease, Type 2 diabetes, osteoarthritis and some cancers.'

Government figures released in January showed that more than one million prescriptions for obesity drugs are now given out to patients.

There were 1.06million prescription items for obesity drugs in England in 2006 - more than eight times the 127,000 figure for 1999.

Dr David Haslam, clinical director of the National Obesity Forum, said: 'The new guidance from Nice is of real benefit to doctors trying to manage this growing group of patients.

'They have got the balance correct, because it will only be used on those patients for whom it will be good. Patients will not be put at risk.'

A recent survey by the International Association for the Study of Obesity showed that Britons are becoming the fattest people in Europe.

English and Scottish women lead the heavyweight league, with almost six in ten overweight or obese.

Men fare little better, with at least two-thirds too heavy for their height.

Fast food, lack of exercise and a growing reliance on time-saving technology are all blamed for making us the second-fattest nation in the developed world. Only the U.S. outranks us.