According to data obtained directly from NHS trusts, some hospitals are now charging as much as £4 for a one-hour stay.
Meanwhile, a third of hospital trusts have increased the average charge over a three-hour period.
On average, analysis of the information by the Press Association has shown, parking charges have gone up by a third between 2014/15 and 2016.
However, there were some exceptions to the trend, given that many hospitals allow patients and visitors to park for free for 30 minutes.
Elsewhere, though, some trusts have abandoned the one or two-hour charge, requiring drivers to pay a standard three-hour fee.
This means that many motorists are being charged the higher rates even if their stay lasts only 45 minutes.
England is the only part of the UK where hospitals routinely charge patients and visitors for parking.
Katherine Murphy, chief executive of the Patients Association, called this “wrong and unjust”.
“These charges can put people off visiting hospital. People on low incomes cannot afford some of the exorbitant charges at these trusts,” she said.
“There is no national policy and all these trusts are doing what they like.
“We acknowledge that many hospitals are in financial difficulty, but making money out of the public in this way is not the answer.”
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Topping the list of the most expensive trusts in England for a one-hour stay is the Royal Surrey County Hospital in Guildford.
Here, drivers have to shell out £4 for any stay up to two hours, though a limited number of bays are provided for free short stays.
Hereford County Hospital in Herefordshire lets people park for free for 10 minutes, but then charges £3.50 for an hour and £5 for two hours.
Meanwhile, the Royal Free Hospital in London charges a flat rate of £3 per hour, 24 hours a day, seven days a week.
Of the 209 hospital trusts that reported figures to NHS Digital for both 2014/15 and 2015/16, a third (69 trusts) showed an increase in their average hourly charge when calculated across three hours.
Some 60% (126) showed no change over the year, while 7% (14) showed a decrease.