The plight of waiting list patients in need of surgery, including cancer operations, is revealed in stark new figures today.
They show hospitals are performing less than half the number of procedures across all specialties they carried out four years ago.
The bleak figures reveal hospitals were operating on 15,374 patients from waiting lists in January 2012, but this plummeted to just 6,743 in January 2016 as they struggled with lack of beds and staff.
It follows the urgent warning by Dr Tom Ryan, president of the Irish Hospital Consultants Association, that cancer patients are now having their surgery cancelled in significant numbers as the crisis deepens.
However, the full extent of the crisis is disclosed in the figures on waiting list surgeries in hospitals which were secured in a parliamentary response by Deputy Jack Chambers, Fianna Fáil TD for Dublin.
He said he was so alarmed by the waiting lists spiralling to more than 630,000 that he investigated the performance of each hospital over four years.
"The results are staggering. In December 2012, hospitals carried out 13,330 surgeries on waiting list patients. But in 2015 this had dramatically fallen to 7,492," he said.
The drop in surgeries has affected patients needing a full range of procedures, including cancer.
"What we are seeing is a haemorrhaging and a halving of output and delivery. At the same time budgets are increasing," Mr Chambers said.
"There has been a dramatic collapse in the number of surgeries while Health Minister Simon Harris continues to talk about bigger budgets. We need to know where the money is going and why it is not delivering."
The breakdown reveals that while there are fluctuations in output over several months, several hospitals which are designated "centres for excellence" for cancer patients are among the worst hit.
Cork University Hospital operated on 603 patients in January 2012 but this was down to 442 in the same month in 2016.
The figures are expected to be even worse for 2017 as it faced unrelenting trolley gridlock most days.
Dr Ray Walley, a GP in north Dublin, said he was seeing some patients who had "red flags" due to the seriousness of their condition but they are suffering cancellations in neurosurgery due to lack of beds.
"There is now a two-year wait for neurosurgery.
"I was told in one hospital recently a staff of 40 were standing around but they were only able to carry out two procedures between them.
"I was speaking to a surgeon who returned here from the UK but he is in talks about going back because he is not doing enough surgery to maintain his skillset."
The Irish Cancer Society yesterday wrote to Dr Jerome Coffey, head of the HSE's cancer control programme, to carry out a swift investigation into the delays highlighted by the Irish Hospital Consultants Association.
"Cancer patients experiencing delays in treatment undergo significant additional stress and upset and this may impact their recovery," said Donal Buggy, the charity's head of advocacy.
It called for each hospital group to address the surgical delays immediately.
A spokeswoman for the HSE said hospitals scheduled patients based on their individual clinical needs and priority as determined by the team caring for patients. Maintaining scheduled care access for all patients and managing emergency demand at times is challenging, however all efforts are made to limit cancellations.