NHS hospitals are making up to £1.85m a year each in profit from charging patients and their families to use their car parks, and from clamping and issuing fines, a report has found.
In England, each hospital decides how much it wants to charge for parking, and the total raised is more than £100m a year.
A study of 126 NHS trusts and hospitals in England found Epsom and St Helier University Hospitals NHS Trust in Surrey made the most money from its car park, making £1.85m in 2008-09 and clamping 1,671 vehicles.
Leeds General Infirmary (part of the Leeds Teaching Hospitals NHS Trust) issued 10,330 fines, generating £142,000. Barnet and Chase Farm Hospitals NHS Trust in Hertfordshire had the highest minimum charge – £4 for two hours of parking.
The consumer group Which? wrote to 172 NHS organisations using the Freedom of Information Act and 126 responded. Hospital car parking is free in Scotland, Wales and Northern Ireland.
In September last year Andy Burnham, who was Health Secretary, announced that hospital car parking charges for in-patients and their visitors would be scrapped within three years, but the coalition Government has no current plans to carry that through.
A spokeswoman for the Department of Health said the issue was still being looked at.
She added: "We can't be in favour of decentralisation and greater autonomy for NHS and then tell them how to run their car parking.
"But it's clear that, where parking charges are making it difficult for staff to do their jobs properly, where they are damaging patients' access to services, or where they are stopping friends and relatives from visiting, they are too high, and hospital trusts have a responsibility to look at those factors."
Professor Stephen Glaister, director of the RAC Foundation, said: "The car is often the best, and sometimes only, way for people to travel to hospital, and managers need to understand the reality of the way people get about.
"If a trust must charge for parking and needs to differentiate between patients, visitors and staff, then there are many ways to do this.
"It is quite possible for bona fide patients and visitors to park free while other car users pay a reasonable amount."
Laura Keely, campaigns manager at Macmillan Cancer Support, said the average cancer patient travelled 53 times to hospital and spent £325 on car parking charges.
Which? named the Royal United Hospital Bath the best NHS hospital car park in England for offering patients, their friends and family a large number of priority spaces as well as a choice of payment methods.
Which?'s chief executive, Peter Vicary-Smith, said: "Visiting hospital is stressful enough without having to worry about being clamped or getting a ticket. Surely this is now the end of the road for the worst hospital car parks?"