However, the US Government-backed research also found that the implants are not completely safe.

Following a study of all available evidence, a committee appointed by the Institute of Medicine, the medical arm of the National Academy of Sciences, said that women with silicone breast implants are not more likely to develop chronic disease than women without implants.

The committee issued a statement saying: "There is no evidence to suggest that the silicones used in transplants are toxic to humans."

However, committee chairman Stuart Bondurant, of the University of North Carolina said that although there was no evidence that the implants could cause life-threatening illness, it was clear that they could cause some problems.

He said: "It is essential that women fully understand these risks before they decide to undergo this surgery."

The committee looked at hundreds of studies and heard evidence from experts, women who reported health problems and from companies that make the implants.

It concluded that most of the risks came from the trauma of surgically implanting extra material into the breast.

The most serious documented problems came from the tissue around the implants contracting, the implant itself rupturing, or an infection developing.

Severe reactions

The report also noted that women often found the implants uncomfortable and had them removed.

Many women had alleged that the silicone used in the implants, which makers says is chemically inert, actually caused severe reactions in their bodies.

They said it leaked out and left them with a range of complications, from cancer to lupus, a serious disease of the immune system.

But the Institute of Medicine committee failed to find any hard evidence that this was the case.

"There is no established link between implants and a unique disease syndrome," the report said.

"Syndromes of the type ascribed to implants generally involve symptoms that are nonspecific and common to the general population."

The 13-member committee of doctors, nurses and other experts also said they failed to find anything showing that silicone can damage the immune system.

But the report did note that many women felt they were not given enough warnings about the possible dangers of implants and said the implants could interfere with mammograms, which are used to screen for breast cancer.

Dow Corning, once the world's largest maker of silicone gel implants, filed for protection from creditors in May 1995 after it was hit with thousands of lawsuits from women alleging the implants caused health problems.

Earlier this month some of the claimants approved a Chapter 11 bankruptcy court reorganization plan for Dow Corning.