Prof Robin Taylor, of the University of Otago Medical School, has spoken out against voluntary euthanasia, telling university graduates that arguments for this were ''fundamentally flawed'', though they might be ''subtly tempting''.
An internationally respected researcher in respiratory medicine, Prof Taylor reminded graduates of the Hippocratic Oath and urged them not to ''contribute deliberately'' to the death of a patient, even if this became legal.
Labour MP Maryan Street is promoting an ''End of Life Choice Bill'', as a private member's initiative, which would allow voluntary euthanasia, with a series of safeguards.
Prof Taylor urged each of the graduating doctors ''when the time comes, as it probably will'' to refuse to ''contribute deliberately'' to the death of any patients.
''I beg each of you to have the courage to stand firm and uphold that core commitment of our professional lives, which is to save life when we can, to relieve suffering when we cannot, and never to contribute deliberately to the death of any of our patients''.
He noted that the modern medical ''oath'' was based on the Hippocratic Oath, which had said, in its original form: ''I will give no deadly medicine to anyone if asked, nor suggest any such counsel."
Addressing about 260 graduates, mainly with qualifications in medicine and medical laboratory science, at the Regent Theatre, Dunedin, at a 1pm ceremony on Saturday, Prof Taylor said he had spent the past three years involving himself in end-of-life care and the need to do it better.
Public discussions about advanced care planning were bound to increase and that was good.
''However, let us be clear: arguments in favour of ending the life of a sufferer as a means of eliminating suffering are fundamentally flawed, even though they may be subtly tempting.
''They are just as flawed as the argument that Hiroshima and Nagasaki [atomic bomb targets] were justified in order to shorten the Second World War.
''The landscape of geopolitical relationships changed irrevocably with the advent of nuclear weapons.
''So, too, the relationship between doctors and their patients would be irrevocably changed, especially for the elderly, if legislation to facilitate assisted suicide were to be enacted.
''This view is not just my own, but is the position held by the New Zealand Medical Association."
He urged graduates to take a generous approach to public service, including in developing nations abroad.
But he warned his ''young colleagues'' they were about to enter a professional world that was often ''shaped by self-preservation'' - also called ''covering your butt''.
As well as in individuals, this phenomenon was found in institutions, and he referred to ''those forces'' that operated in hospitals and universities, and in every other large human organisation, to ''make us behave differently when we are part of a bigger machine, to suppress our consciences and to blunt our willingness to be compassionate''.
''It is a tragic mystery that when human beings get together as an organisation, we become collectively conditioned to be much less humane."
He reminded graduates of the biblical parable of the Good Samaritan.
The Good Samaritan had not only shown compassion in stopping to help the stricken traveller, but ''more than that, he had guts''.
He urged graduates to ''have the moral courage to take risks for the sake of others''.