Patients in need of chemotherapy are being forced to wait up to five weeks because the St George Cancer Centre does not have the resources it needs to deal with increasing demand.
St George is one of the busiest cancer centres in the state, but doctors say it is still operating with the same resources it had when it opened 20 years ago.
Senior medical staff say the problems at the cancer centre are symptomatic of a much bigger problem, and are calling on the government and the local health district to urgently reassess the way money is allocated.
The head of radiation oncology at the hospital, John Kearsley, said forcing patients to wait up to five weeks for chemotherapy, and sometimes even longer for radiotherapy, could put them at risk.
"The delays could affect the efficacy of treatment," he said. "And people get very frustrated - if you've got breast cancer and were told you would have to wait four to six weeks for treatment, imagine what you would think."
He said the hospital still had the same number of chemotherapy rooms and radiotherapy machines as it did when it opened in 1993.
Professor Kearsley said the hospital had become reliant on donations from the local community, with a recently opened prostate cancer centre - the most comprehensive such treatment facility in the state - funded by donations.
"There is really no certainty in the funding situation from the Department of Health," he said.
A senior medical oncologist at the hospital said the cancer centre was "no longer fit for purpose".
The chairwoman of the St George medical staff council, Theresa Jacques, said the hospital had half the number of operating theatres and intensive care beds a hospital of its size should have.
"We had double the number of major trauma patients in 2013, compared to 2012," she said.
The acting clinical group manager of surgery at St George and Sutherland Hospitals, Andrew Bridgeman, confirmed the average four-week wait for chemotherapy. But he said patients had only increased by 6 per cent this year, in line with other services.
"Waiting times at other cancer centres have seen additional patients from outside our area accessing cancer services at St George," he said. "Staff vacancies have also impacted on the waiting time."
He said there were plans, funded by both the community and government, to renovate the centre.
St George's budget has been increased by $12 million this financial year.