Under 100 organ transplants were carried out in the UK last month, the lowest number for 36 years figures show.
NHS Blood and Transplant (NHSBT) analysis for BBC 5 Live Investigates showed there were 99 operations in April, down from 244 in March.
The last time the monthly total dropped below 100 was February 1984.
Some specialists fear the fall in the number of operations will cause a backlog of patients needing organ donations, leading to increased waiting times.
Prof Peter Friend, director of the Oxford Transplant Centre, told the BBC Radio 5 Live Emma Barnett show: "Every transplant that does not take place now means that a patient somewhere, and at some point, never receives their transplant.
"This is an inevitable consequence of the fact that the supply of donor organs does not meet the demand.
"Even before the coronavirus epidemic, patients were dying on the transplant waiting list, and the effect of doing fewer transplants during the crisis means that this mortality rate must increase."
NHSBT say that activity – which includes operations such as kidney, heart and liver transplants – has increased to 47 per week at the beginning of May up from 10 at the start of April.
'I was told – don't expect a transplant'
Sunaina Paul, 31, from Birmingham has been on the super-urgent waiting list for a liver transplant for the past 13 months and is reliant upon antibiotics to prevent infections in her liver.
Last month she was told by her consultant to not expect a transplant during this period.
"I feel really disheartened by it. I've waited 13 months, I've put my life on hold."
"If I become immune to these antibiotics then I'm really going to be struggling and will need to be admitted into hospital. Even now, at the moment I've got a liver infection, I'm in pain all the time,
"I feel sick…I can't eat properly."
The new data shows that just 206 patients were added to the waiting list in April, down from 524 in March.
Until people are assessed and put on the waiting list, they cannot be considered for a transplant, meaning a delay in assessment could leave patients waiting longer for a new organ.
'A worrying time'
During the coronavirus crisis, capacity has been directed towards patients in most urgent need of transplantation and some centres have closed.
On one date last month, just six of the 24 kidney transplant centres were open, although all liver, lung and heart units remained open.
There has also been further pressures on the supply of organs.
Patients who tested positive for coronavirus cannot Read More – Source