Hospitals collect €60,000 a day in parking charges, according to new figures from the HSE.
The data revealed by Newstalk this morning shows €22.4m was received by hospitals around the country in 2017.
Sinn Fein's Health Spokesperson Louise O’Reilly, who obtained the data through a parliamentary question, said it is an unfair charge on people who have no choice but to attend hospital.
Ms O'Reilly said: "The figures from the Irish Cancer Society who have surveyed their own patients, and obviously, these are people who absolutely have to be in hospital regularly, they have estimated that cancer patients are paying up to €63 a week in car parking charges.
"So, at a time in their life when their income is restricted, when they are sick and when they can really, really least afford it, and they need the burden the least, they are being asked to stump up €63 a week."
In its reply, the HSE said the majority of hospitals around the country charge for parking with just nine offering the service for free.
Of the 47 hospitals that charge for the service, some 16 use an external third party to manage the car parks.
Cork University Hospital makes the most money in the country through car parking charges – pulling in €3.1m in 2017. The hospital is one of only two in the top 10 that manages its own car park.