However, some experts have labelled the claims misguided and irresponsible and fear the debate will alarm organ donors and the wider community.

Associate Professor James Tibballs, a pediatric intensive care specialist at the Royal Children's Hospital, has called for a review of organ donation guidelines to ensure donors know that their organs can be taken when they are dying and not yet dead.

In a controversial article, published in the Journal of Law and Medicine this month, Dr Tibballs said clinical practice clashed with the law, which says organs can be taken from a donor when they have either irreversible cessation of all functions of their brain or irreversible cessation of blood circulation.

Dr Tibballs said clinical guidelines commonly used to diagnose brain death could not prove irreversible cessation of all brain function, and that the concept of brain death introduced into Australian law in 1977 was a "convenient fiction" that had allowed the development of organ transplantation.

Dr Tibballs also argued that when organs were taken after cardiac death (defined as the absence of blood circulation) it was usually done when the heart failed to restart itself for two minutes, not when proven "irreversible cessation" of its function had occurred.

This two-minute time limit was set partly because there is a limited time for organs to remain viable when someone is dying, he said.

Furthermore, Dr Tibballs said some interventions to ensure the viability of organs could actually harm or cause the death of the donor.

"The question of when is it permissible to retrieve organs is now phrased not in terms of whether death is present or not, but rather 'how dead is enough'," he said.

Despite donors being told by government organisations that they will be "brain dead" when their organs are taken, Dr Tibballs said donors were usually very close to death with no chance of survival during organ procurement.

He said he was not suggesting some patients could be brought back to live meaningful lives when their organs were taken, but rather wanted donors to know exactly what could happen to them so that they could give informed consent.

To improve the certainty of brain death diagnosis for organ donation, Dr Tibballs also called for a test of blood flow to the brain, which is currently optional and available in most hospitals, to be made compulsory.

He said the definition of death had previously troubled doctors, and that it was disturbing that some of these doctors were involved in the certification of death for the purposes of organ donation.

"It could be troubling for the public to realise that doctors looking out for organ donors are also the ones formulating guidelines on how to declare death for organ transplantation," he said.

"For this reason, there should be members of the community and people with legal backgrounds on the committee that create these clinical guidelines used to declare someone dead."

Dr Tibballs' argument comes three months after Prime Minister Kevin Rudd, who had a heart valve transplant from a donor, announced a $136 million plan to increase organ transplantation, including the creation of a national donation authority and more organ transplant doctors.

But some intensive care specialists have branded Dr Tibballs' comments irresponsible because, they say, he is debating a technical medical point that could cause organ donation rates to plummet if the debate is misunderstood by the public.

"This could be very damaging to public confidence of brain death diagnosis, because a lot of people might say, 'we don't believe in this any more,' and as a consequence, people might die on waiting lists," said Associate Professor Bill Silvester, medical director of LifeGift, and senior intensive care specialist at the Austin Hospital.

Professor Geoffrey Dobb, chair of the Australian and New Zealand Intensive Care Society's committee on organ and tissue donation, said the committee had already rejected Dr Tibballs' call for a mandatory blood flow test to diagnose brain death, because current guidelines had been 100% accurate.

He said Australians could have absolute confidence that if they were diagnosed as brain dead - whether or not it was for organ donation - they would be dead.

"I strongly emphasise that this (Associate Professor Tibballs') view is an extreme minority point of view," Professor Dobb said.

"We know that every organ donor potentially saves or greatly enhances the lives of up to six other people, so even the loss of a single donor or someone who wished to be a donor is a major loss to the community as a whole."

But the clinical director of the Northern Hospital's Critical Care Department, Dr Graeme Duke, said Dr Tibballs had identified ambiguities in the organ donation process that needed to be fixed.

He said guidelines for organ donation should be revised to eliminate legal risks and ensure informed consent from donors.

"Australia has some of the best outcomes from organ transplantation in the world and we want to maintain that and improve the quality of the standards and guidelines," Dr Duke said.