The British Medical Association (BMA) said it was time for a serious debate on the issue.
About 650 people north of the Border are on the waiting list for a transplant but some will die before the chance of a new organ.
Dr Sue Robertson, a renal physician and a member of the BMA's Scottish Council, said: "It is important that an individual's views on organ donation are taken into account following their death. A soft opt-out system would better reflect the views of the Scottish people."
The BMA has long called for a soft opt-out system, arguing such a change could save or transform thousands of lives.
It would mean that when someone who had not opted out of being a donor died, their relatives would be asked if they objected to their organs being used to help others.
Gill Hollis, who received a lung transplant, also backed a move to an opt-out system. The Edinburgh woman said: "I wouldn't be here today without my transplant, so I am incredibly grateful to my donor family; their generosity saved my life. But I was one of the lucky ones – I received my transplant in time."