A London surgeon has been given the go-ahead to carry out what could be the world's first full-face transplant.

Patrick Butler, of the Royal Free Hospital, hopes to carry out the operation within months and is already in the process of selecting the first patient to undergo the procedure.

Mr Butler, who has spent 15 years developing plans for face transplants, said that he was "delighted" to finally win permission for the surgery from his hospital's ethics board. He said: "It's been a long journey but this is just the beginning, really. The most important part of the process starts now, which is selection of the patients."

The board took into consideration the major ethical and psychological implications of giving someone a dead person's face, along with the consequences of transplantation rejection, before agreeing to the process.

More than 30 potential candidates in Britain and Ireland have now been identified and from them, four will be selected for the first transplants.

Last year, a French team carried out the world's first partial face transplant on 38-year-old Isabelle Dinoire, whose nose, lips and chin were torn off when she was mauled by a dog.

That operation has been hailed a success, with Ms Dinoire regaining sensation in her new face. She said that she had been "saved" by the surgery.

Mr Butler said that the prospective patients will be adults with severe facial injuries who had already undergone scores of operations with little success.

"They have reached the end of the reconstructive ladder and there's nothing more it can offer them," he said. "They have the problem of integration into society, of being able to walk down the street in society without anybody staring at them. That's what these people want - to be normal."

Once patients have been identified, they will then have to wait for the death of someone who has agreed to donate their face and is an appropriate match.

The 12-hour transplant operation will involve removing skin, fat and various blood vessels, arteries and veins from the donor, before the face is connected onto the recipient.

After the operation, the patient will have to take immuno-suppressant drugs for the rest of their lives to help prevent rejection of the new tissue.

Research among the public has shown a high level of support for face transplants.

The major concern that has emerged from surveys is that the family of a donor may see a transplanted patient walking down the street with the dead person's face.

Mr Butler said that traits such as skin colour will be transferred but computer modelling showed that facial characteristics following transplant are mostly those of the recipient rather than the donor. The main reason is that the skin is very pliable and falls across the existing bone structure and cartilage of the person receiving the face transplant.

Mr Butler hoped transplants would become the first choice in reconstructive surgery - but this scenario was a "long way off".

Experts welcomed the news, but advocated caution for the future. Changing Faces, the national charity for people with facial disfigurement, said: "Our main concern is to ensure that any patient who is being considered for this procedure has a full understanding of the risks and benefits, especially the risks associated with the immuno-suppressant drug regime."