The Royal College of Surgeons has urged doctors not to carry out facial transplants.
Surgeons say they could now carry out a face transplant
In a report, it said that while the skills and knowledge exist it would be unwise to proceed without further research into the risks.
But they said they were "not adverse" to the surgery and recognised it as a possible future treatment.
The report comes a week after surgeons revealed they were now able to carry out the operation due to advances in the use of anti-rejection drugs.
Doctors in the US and France are awaiting regulatory approval to carry out the operation.
British surgeons say they will not carry out the procedure until the public has debated the ethical issues around it.
But the royal college report advises doctors against carrying out a face transplant, saying the physical and psychological effects are unknown.
"Until there is further research and the prospect of better control of these complications, it would be unwise to proceed with human facial transplantation," it says.
Professor Sir Peter Morris, the college's president, said: "The micro-surgical skills and anatomical knowledge required to carry out facial transplantations are already well established.
"But facial transplantation is not only a question of technical achievement.
"We must also take into consideration the psychological impact on the recipient and on the donor family, and the considerable long-term risks of the need for lifetime immunosuppression drugs."
He suggested that large scale animal studies are needed before the treatment should be made available.
Consultant plastic surgeon Michael Earley, one of those involved in the report, backed that view.
"Facial transplants are one of the most exciting possibilities that have come along in a very long time," he said.
"But there is a lot of work to be done too."
The procedure would involve removing facial muscles and skin from a dead donor and placing them on a living person.
It is clearly controversial. Surgeons have acknowledged they will need public support to carry it out.
British surgeon Peter Butler, who is one of those who could carry out a face transplant, welcomed the report.
"What they have said is it would be unwise to proceed with facial
transplantation at the moment, which we would agree with.
"There are a number of issues, psychological, immunological, moral and ethical questions that need to be answered and fully explored before proceeding.
"The most important thing for us is to sort these things out before any procedure takes place.
"For facial transplantation to take place before this is done would be a step backwards rather than a step forward."
Dr John Barker, an American plastic surgeon from Louisville University in Kentucky, will address a public debate on the issue later on Wednesday.
Speaking earlier he said he was ready to carry out the world's first face transplant.
"We believe we are ready," he said.
Dr Barker said he could not and would not name a date when the first face transplant would be carried out because it would create unnecessary media
However, he said the world-wide search had already begun for a suitable person on whom the first operation could be carried out.
James Partridge, chief executive of the charity Changing Faces who was severely burned in a fire when he was 18, said more research is needed before any operations can go ahead.
"Psychologically, I think face transplants are very different to having somebody's kidney or liver," he told the BBC.
"To take somebody's face is to take part of their identify and to lose part of yours."
He added: "I would certainly want a lot more research into what the impact of that would be."
Mark Crank, who is facially disfigured, said he would never consider having a transplant.
"I don't think there is anything about my appearance that I would desperately want to change," he said.
"It's not about changing my face, it's about changing people's attitude to my face."