NHS hospital trusts have been accused of levying a "tax on sick people" after an investigation revealed some are making more than £3 million a year from car parking fees.
Year on year, hospitals across England are raising increasing amounts of money from staff, patients and visitors, including those who are disabled, the Freedom of Information study by the Press Association found.
Hospitals are also handing over millions of pounds to private firms to run their car parks for them, and allowing some to cash in on parking fines.
Others are tied into private finance initiative (PFI) contracts, where all the money raised from charging ill patients, staff and visitors goes to private firms under lengthy contracts.
Of more than 90 trusts that responded to the FoI request, half are making at least £1 million a year.
Seven NHS trusts earned more than £3 million in 2014/15 from charges, a further eight made more than £2 million a year while a further 33 earned more than £1 million a year.
Almost half of all trusts also charged disabled people for parking in some or all of their disabled spaces.
Katherine Murphy, chief executive of the Patients Association, branded the charges "morally wrong".
She said: "We are concerned that hospitals in England still charge patients for car parking.
"Why is it that patients in Wales and Scotland do not have to pay to park? It is a postcode lottery and a tax on sick people who sometimes struggle to pay.
"The money is never reinvested in frontline services. Hospital car parks are often managed by private contractors who take a huge percentage of the profits.
"This is morally wrong - and charging disabled people is a disgrace."
Rosie Downes, senior campaigns officer at Macmillan Cancer Support, said: "The core principle of the NHS is to provide free healthcare for all at the point of access.
"But sadly these latest figures show that some cancer patients in England are still paying extortionate hospital car parking charges in order to access treatment for a life-threatening illness.
"Cancer patients receiving vital treatments such as chemotherapy and radiotherapy will often need to make frequent trips to hospital and unaffordable charges are leaving many out of pocket."
Many trusts defended their revenues, saying some or all of the money was put back into patient care or was spent on maintaining car parks or grounds.
Others claimed their sheer size and the fact that they serve busy neighbourhoods meant they took more in revenue.
University Hospitals of Leicester NHS Trust raised £3,126,108 from car park charges in 2014/15, up on the £3,002,865 in 2013/14. Since April this year, it has taken an additional £1,316,539.
Meanwhile, Sheffield Teaching Hospitals NHS Foundation Trust raised £3,160,913 in 2014/15, up on the £2,977,109 in 2013/14.
The Heart of England NHS Foundation Trust took £3,413,413 in car park charges in 2014/15. This was less than the previous year, but up on the £2,788,293 in 2011/12.
And Oxford University Hospitals NHS Foundation Trust raised £3,728,000 net in 2014/15, of which it listed £2,957,000 as "costs" such as running the car park office, security and legal fees.
The investigation found that some hospitals were built under PFI contracts, with all money from parking going to private companies under the terms of the scheme.
At the London North West Healthcare NHS Trust, £1.8 million in 2014 went to the firm Apcoa. It manages the Northwick Park multi-storey under a PFI contract.
Apcoa pays the trust around £40,000 a month on a lease basis, the trust said. The firm also kept £34,052 in parking fines in 2014.
Wye Valley NHS Trust has a PFI contract until 2029, and all its money from patient, visitor and staff parking goes to PFI partner Mercia Healthcare.
Some NHS trusts also raised a significant amount from charging staff for parking. University Hospital Southampton NHS Foundation Trust took £3,876,314 in parking charges in 2014/15, of which £1,206,836 was from staff.
The Mid Yorkshire Hospitals NHS Trust made £424,000 in visitor pay and display income in 2014/15, plus £549,000 from staff parking.
Meanwhile, Northern Lincolnshire and Goole NHS Foundation Trust made £2,159,000, including £22,000 in parking fines and £327,000 from staff.
Shadow health minister Andrew Gwynne said: "When patients go to hospital, the last thing they want to worry about is keeping the car parking ticket up to date. For some patients and their families, the costs can really rack up, which is why these figures are so worrying.
"The last Labour government had a plan to phase out car parking charges, but recent attempts to discuss this matter in Parliament have been blocked by Tory MPs."
A Department of Health spokeswoman said: "We expect all NHS organisations to follow our guidelines on car parking, including offering discounts to disabled people.
"Patients and families shouldn't have to deal with the added stress of unfair parking charges and our guidance rightly helps the public hold the NHS to account for any unfair charges or practices."
Josie Irwin, head of employment relations at the Royal College of Nursing, said: "Nurses regularly work late nights and weekends, and as a result already have to deal with extra costs such as childcare. If they then have to pay excessive charges for car parking it makes a real impact on their pay, which has already fallen far behind the rate of inflation."
RAC spokesman Simon Williams said: "Our research shows that almost nine in 10 motorists (88%) think parking in hospitals should be free - this view is even more prevalent among those aged 65 or older (93%)."