The number of people spending Christmas on the heart transplant waiting list has gone up by a quarter since last Christmas.
Those waiting for a transplant include 33 children who will spend the Christmas period seriously ill.
The serious situation has led to NHS Blood and Transplant to call out to the public to join the organ donor register, so that when they die their organs can be used to give life to others.
For most patients on the heart transplant waiting list, all other medical options have already been exhausted, and a donated organ is their only hope.
Since last Christmas Day, 31 people have died while on the waiting list for a heart transplant.
But those who do receive a heart transplant can expect to live for another 14 years on average, with some living an extra 30 years.
There are currently 298 people on the waiting list for a heart transplant compared to 240 people at the same time last year - a rise of 24%.
The Department of Health recently launched a consultation into an “opt out” system of organ donation for England, rather than the current “opt-in” so that people do not have to remember to sign up.
Sally Johnson, NHS Blood and Transplant director of organ donation and transplantation, said: “Hundreds of people are spending Christmas waiting for a call that might never come. Their families will be spending the festive period living with fear and uncertainty.
“We desperately need more people to agree to donation to help with the number of people waiting for hearts and organs of every kind.
“Whatever the outcome of the Opt Out consultation, if you support organ donation, please act today.
“Tell your family you want to donate and join the NHS Organ Donor Register.”
Steven Tsui, consultant cardiothoracic surgeon at Papworth Hospital NHS Foundation Trust and chairman of the NHS Blood and Transplant Cardiothoracic Advisory Group, said: “The UK heart transplant waiting list has been growing year on year.
“A lot of people who could donate do not discuss their wish to be an organ donor with families and friends. When they die, their organs simply go to waste.
“Heart transplant is the most amazing treatment for patients with advanced heart failure. The transformation is quite miraculous.
“On average, a heart transplant recipient can expect to live for another 14 years; the lucky ones could even get 25 or 30 extra years.”