It is 30 years since Christiaan Barnard carried out the first organ transplant, yet the UK still has no rules for who gets treated - and who is left to die

For nearly three decades, surgeons have been saving patients on the verge of death thanks to organ transplantation. These days, the pioneering work of Christiaan Barnard is almost routine but still miraculous for those lucky enough to receive a new heart, lung or liver. Yet the reasons why some are chosen and others are turned away remain shrouded in secrecy. It is extraordinary that those refused a transplant typically accept the decision without rancour. They certainly do not contest it publicly. And then, usually, they die.

The case of 15-year-old Michelle Paul, the teenage drug user who died after being refused a liver transplant, has, however, thrown a rare spotlight on the Godlike powers doctors retain in determining which patients receive the small, limited supply of vital transplant organs - and who dies. Even now, few people appreciate the lack of rules governing these powers.

Christianity's God promises eternal life if you abide by 10 clearly defined commandments, but there are no such national guidelines to inform a dying person what is required to qualify for a new liver, heart, lung or kidney. Without such rules, it is difficult to seek judicial review of a doctor's decision. So unless transplantation from pigs is perfected and offers a plentiful supply of replacement organs, patients must place their hopes in the paternalistic hands of the doctors whose preferences control this particular lottery.

You might think qualification depends on being next on the waiting list or on being seriously ill or on being young or having dependent children. Doctors certainly consider these factors. They take extremely seriously the responsibility of deciding between competing claims. But there is no formal points system, which, though imperfect, would at least be transparent and contestable. In practice, the final decision is left to a doctor's discretion by the United Kingdom Transplant Support Services Authority, a doctor-dominated body which oversees the system for the NHS. Doctors alone decide whether someone is even put on the waiting list.

There is, therefore, little to prevent a surgeon from choosing to give little Johnny a new liver because his dad is an old friend from university and the surgeon couldn't possibly let him down. If a surgeon behaved in this way, the public would not discover his reasoning because there is no legal requirement upon doctors to explain why they gave one patient an organ and turned down another. The authorities judge that such decisions - and even the people who make them - are best kept out of the public gaze.

This hidden, unaccountable world is typical of a health service that refuses to involve the public in the rationing of health care. It has disturbing echoes of Michael Crichton's 1978 fantasy thriller Coma in which comatose patients are used as donors for organ transplants. At the denouement, Richard Widmark, the chief surgeon at the centre of the plot, protests that he and his colleagues behave like gods because neither the public nor politicians are willing to face the hard issues raised by medical advances.

This much is certainly true of the British transplant programme, according to a research project just completed during a British government-sponsored Atlantic Fellowship by Jeffrey Prottas, Professor of Public Policy at Brandeis University, Boston. Dr Prottas has discovered that there is no easy way to check that organs are being used equitably. Socio-economic data on those given organs - and those denied - are not collected. So we do not know if selection for transplant is biased in terms of race or class. One can only rely on a suspicion that a system run largely by white, professional men will, however inadvertently, benefit their group disproportionately.

"At a local level", says Dr Prottas, "there is no public oversight of what happens to organs. Who's next depends on the physician in charge who may vary from day to day. So Dr Small might have a different set of priorities on Thursdays than Dr Jones does on Fridays.

"The system works. I have no reason to believe that bad decisions are being made under what people in the transplant world call the `club rules'. And the outcomes in terms of survival are as good as, for example, the United States. But sometimes personal compassion can take over from professional judgement. For example, maybe the husband of a senior colleague needed the transplant, so something had to happen."

A further problem with the British system, says Dr Prottas, is that it is difficult to tell whether the NHS gives every region the same chance of transplants. There is little requirement on regions to share non-renal organs, except in an emergency. (One out of every pair of kidneys collected must be offered into a national pool.) So if you live in an area where relatives are reluctant to permit organ donation or where the health authorities are poor at procurement, your chances of survival may be considerably lower when your liver fails than for someone living elsewhere in the country.

The death of Michelle Paul suggests that the UK transplant system, which has long worked within a cosy professional consensus, may be fragile. Like the blood transfusion service, it relies on the trust of the public, which is the source of donated organs. If that trust falls apart, grieving relatives may in future be less generous with the remains of their loved ones.

That danger has already been faced in the US where there are now far more rules than in Britain to determine rights to a transplant. Last year, in a case similar to Michelle Paul's, a woman with Down's syndrome was refused an organ transplant because doctors judged her incapable of maintaining the lifelong drug regime required to prevent rejection. A public outcry provoked a review which overturned that decision - it emerged that the woman, though retarded, held down a job and was responsible. Michelle Paul, before she died, had no such opportunity of a fair and impartial hearing.