'Doctors who sell snake oil pose greater danger to the public than lay persons selling snake oil because the public trusts doctors more,' a ministry spokesman said.

While the treatments - which include firing water into the large intestine and using carbon dioxide to zap cellulite - are not illegal, they are not supported by medical evidence, the spokesman said.

The warning comes as a growing number of doctors branch out into lucrative beauty treatments, some of which have been banned in other countries.

Almost six in 10 Singapore general practitioners (GPs) now do aesthetic procedures, including those that are medically sound.

Specialists in fields such as anaesthesia, gynaecology and even renal medicine are also grabbing a share of the multimillion-dollar market.

Some doctors make over a million dollars a year from the procedures.

The treatments have not been without controversy though.

The Singapore Medical Council is investigating six doctors, including a specialist, following complaints about their aesthetic work. It is believed some performed procedures that the MOH warned against.

Some doctors, however, disputed the view that the procedures were unsafe and questioned the general caution.

Dr David Loh, a GP who has concentrated on aesthetic treatments for the past six years, said: 'There may not be scientific proof, but that doesn't mean it doesn't work.

'The bottom line is that the treatments do no harm, even if they do little or no good.'

Some of the procedures used here, including fat-busting mesotherapy, have been banned in other countries.

Widely available for hundreds of dollars per session, the treatment involves injecting a cocktail of drugs into the patient supposedly to dissolve fat and make the skin smooth.

Reported problems with mesotherapy include skin and joint infections, bruising and inflammation.

The United States Food and Drug Administration does not approve the use of any mesotherapy drugs.

Britain, Canada and Brazil have also banned drugs purporting to dissolve fat, though the procedure is popular in France.

Singapore's KK Women's and Children's Hospital scrapped plans to offer the procedure at its aesthetic centre.

Plastic surgeon Vincent Yeow, the department's head, said: 'We realised there was no scientific basis and the results were not consistent.'

The Health Sciences Authority said these substances have neither been evaluated nor approved, and doctors should 'exercise their professional judgment on the use of unlicensed products'.

The Health Ministry said it is looking into the 'appropriateness and standards' of a range of beauty and wellness procedures.

Meanwhile, it suggested that doctors tell their patients the treatments are experimental and have no scientific underpinning.

The Singapore Medical Association, which represents the majority of doctors here, said last night that it supports 'evidence-based medicine' and looks forward to working with the ministry to 'improve the practice of aesthetic medicine'.

salma@sph.com.sg