Wales has introduced a landmark organ donation law that makes every adult an organ donor after their death, unless they opt out beforehand.
The new rule, which sees anyone over the age of 18 become a potential donor, comes into force today.
It will apply to all adults who have lived in the country for more than 12 months.
It is hoped the system, known as presumed consent, will increase the number of organ donors by as much as a quarter.
Mark Drakeford, Wales' health minister, said:
Some religious groups have criticised the move.
Ahead of the new law several faith groups circulated an open letter, signed by leading Welsh Christian, Jewish and Muslim clerics, expressing their unease about the plan.
It said: "We remain opposed to any weakening of the principle the donation of organs should be free and voluntary."
But among those welcoming the new law in Wales is the British Heart Foundation, which says the rest of the country should follow suit.
Simon Gillespie, the charity's chief executive, said organ donation rates in the UK are 40 per cent lower compared with other countries as Spain and Croatia that already use the opt-out system
"Sadly hundreds of people die every year waiting for a transplant because there is a desperate shortage of organ donors," he said.
Organs from donors under the new system - including kidneys, heart, liver, lungs and pancreas - could go anywhere in the UK.
According to the latest figures, only 8 per cent of eligible adults in Wales have decided to opt out ahead of the new law.