Silicon implants can be problematical

The technique uses fat from the stomach or thigh which is then enriched with stem cells before being injected.

It is hoped the method could prove a more natural-looking alternative to artificial implants filled with salt water or silicone.

But plastic surgeons working in Britain have greeted news of the technique with "extreme caution."

Kotaro Yoshimura, a surgeon at the Tokyo University medical school, said more than 40 patients had been treated.

The enhanced breasts are soft and natural, so they are the patient's "real" breasts

Cellport Clinic Yokohama

Mr Yoshimura said he believed the stem cell and fat combination, which can increase a woman's cupsize by two sizes, was a success.

"There have been no serious complications," he said.

During the operation, surgeons suck fat cells from the stomach or thigh, and this "slurry" is enriched so that there are higher numbers than usual of stem cells.

These are "master" cells which are capable of making new fat cells.

When the enriched stem cell mixture is combined with normal fat tissue, it can then be injected into the breast area.

More natural look

The treatment aims to offer a softer more natural look than traditional silicone implants.

Mr Yoshimura said the he believed combining stem cells with fat gave an improved result.

He said breast enlargement using fat and stem cells did not create a lumpy effect.

Lots of small particles were added rather than "one big lump".

Cellport Clinic Yokohama in Japan are currently the only ones to provide the treatment.

The clinic website claims: "The enhanced breasts are soft and natural, so they are the patient's "real" breasts."

Consultant Norman Waterhouse said he had concerns about such a procedure.

He said: "It would be incorrect to suggest that a breast implant equivalent could grow from stem cells alone, and fat transfer, which is not a new procedure, can still lead to complications and give a lumpy effect."

"This appears to be a rather optimistic view of what is yet a theoretical approach."

Consultant Rajiv Grover added: "We greet this news with extreme caution."

However, Adam Searle, past president of British Association of Aesthetic Plastic Surgeons said the development should not be dismissed.

"There is exciting potential but no reality in practical terms at the moment.

"The stem cell 'soup' is too non-specific to really focus on what you want."