A shift towards a system of presumed consent for organ donation in England has been welcomed by doctors and health charities.
Prime Minister Theresa May said 500 people died last year because a suitable donor organ was not available, as she signalled the move to an opt-out system.
The British Medical Association (BMA) said Mrs May's announcement had the potential to save many lives, while Kidney Care UK said it was a "momentous day".
Mrs May told the Tory party conference in Manchester: "Our ability to help people who need transplants is limited by the number of organ donors that come forward.
"That is why last year 500 people died because a suitable organ was not available. And there are 6,500 on the transplant list today.
"So to address this challenge that affects all communities in our country, we will change that system. Shifting the balance of presumption in favour of organ donation."
The Prime Minister highlighted the fact that members of black and minority ethnic communities had an increased risk of illnesses, including high blood pressure, that may lead to the need for an organ transplant.
BMA council chairman Dr Chaand Nagpaul said: "The decision to introduce an opt-out system for organ donation in England is excellent news.
"The BMA has lobbied and campaigned tirelessly on this for many years and has the potential to save many lives.
"It is important that the new process is well publicised to ensure the public are fully aware of and understand this important change.
"The health service must also have the resources, as well as facilities, to ensure transplant procedures can be performed when they are needed."
Fiona Loud, policy director at Kidney Care UK, said: "This is a truly momentous day for the 25,000 people in England on dialysis with kidney failure.
"One person dies every day whilst waiting for a kidney transplant and this change has the potential to be both life-saving and life changing."