Health leaders have warned of a "sharp" decline in organ donations, with "urgent action" now required to help 8,700 people waiting for a transplant.
NHS Blood and Transplant (NHSBT) has called it "one of the most challenging periods for organ donation in over a decade", with work under way to determine the cause.
Deceased donation rates are currently 9% below this time last year, and family consent rates fell from 67% in 2020/21 to 57% last year.
NHSBT has since launched an "urgent response plan" to address the decline.
Anthony Clarkson, the organisation's director of organ and tissue donation, said: "We are facing one of the most challenging periods for organ donation in over a decade. The sharp decline in donors and the rising number of people waiting for a transplant need urgent action.
"We have already adapted significantly to changes in the donation environment, but saving lives and reducing the waiting list needs collective effort across the NHS and society.
"There is a simple action the public can take to help save lives. Please sign the NHS Organ Donor Register. Most of us would accept an organ if we needed one but opportunities to save lives are being lost because families didn't know what their loved ones wanted. Leave them certain."
Nicola and David Lee consented to donate their daughter Miriam's organs after she died aged just 17 from sudden cardiac arrest.
She had previously registered to be a donor and her liver was given to Ollie Jolliff, from Dorset, who required a transplant at 11 months old in 2016 due to a genetic condition.
They called it a "true honour" to see Ollie - who is now 10 - grow up.
His mother Hannah Jolliff said: "Ollie knows he's got a special liver, and he knows that Miriam is the special girl who gave it to him.
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"We're so aware of how different things could have been had Miriam and her family not made the decision to donate. It was a difficult and completely selfless decision, and we are so grateful to them.
"Organ donation is something very special. It can completely change the lives of people like Ollie and us, as his parents. We'd urge everybody who can to consider what their decision would be and to confirm it on the NHS Organ Donor Register."
Organ Donation Week, which aims to raise awareness about the benefits of organ donation, began on Monday.
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