Car park charges in Welsh hospitals are an "immoral" tax on the sick and should be abolished, senior doctors have said.
The Welsh NHS Federation says charges "manage demand"
Dr Richard Lewis, Welsh secretary of the British Medical Association (BMA), said the charges were an "indirect tax" on healthcare.
At least a quarter of Welsh hospital trusts are drawing a six-figure income from parking charges, the BMA said.
The Welsh NHS Confederation said the charges were about managing demand not making a profit out of patients.
Many of the trusts contract out car park management to private companies.
The BMA claimed that Swansea NHS Trust received more than £1m from parking charges last year, making a profit of £443,810.
North Glamorgan NHS Trust and Velindre NHS Trust do not charge patients to park on their premises.
Income from charges in Cardiff and Vale NHS Trust go to private contractors Vinci, who run its car parks.
Dr Lewis said: "Charging people to park at hospitals is an indirect tax on healthcare. These days, the vast majority of people who attend hospital clinics do so by car.
"Often, these people have to attend several times during treatment and the costs mount up. It's iniquitous that they have to pay to access hospital care.
Dr Lewis said public transport was often inconvenient for patients who had mobility problems.
"This stealth tax is immoral and reprehensible. For visitors, or anyone going to hospital, the last thing you want to be doing is worrying whether you have money in your purse to put in the meter," he added.
CAR PARK INCOME 2005/2006
Swansea NHS Trust: £443,810
Bro Morgannwg NHS Trust: £650,000
Gwent Healthcare NHS Trust: £466,000
Ceredigion and Mid Wales NHS Trust: £11,816
North Glamorgan NHS Trust: Free parking
Velindre NHS Trust: Free parking
Cardiff and Vale NHS Trust: Revenue goes to private contractor
Source: British Medical Association. Figures are income and not profit.
BMA Welsh Council chairman Dr Tony Calland also called the charges a "tax on the sickest patients and their relatives".
"The most ill section of the population has to visit hospital more frequently than those who are healthier and it is often these very ill people who, because of their illness, are the least able to pay the substantial car parking charges," he said.
"The founding principle of the NHS was that healthcare should be free at the point of delivery."
The Welsh Assembly Government said parking was a matter for individual trusts who take into account a number of factors - such as patients' needs and public transport - when deciding what facilities to provide.
Mike Ponton, director of the Welsh NHS Confederation, which represents all the NHS organisations in Wales, said it was up to individual trusts to decide on car parking policy.
He said: "Many NHS hospitals have a very limited supply of space. At the same time, the demand for car park spaces keeps increasing.
"Providing free parking for all could mean that patients and visitors cannot park because spaces are being used by unscrupulous people who take advantage.
"On occasions, increasing congestion has even made it difficult for ambulances to access hospital entrances."
He added many hospitals had schemes where patients receiving ongoing treatment could park free or at a reduced rate.
"It is important to understand that this is not about making a profit out of patients it is about managing demand," he added.