Health chiefs say the £3.20-an-hour parking charge at Northampton General Hospital is essential to free up money for care after it was revealed to have the second-highest tariff in the country.
A series of Freedom of Information requests by the Mail Online has found that Royal Surrey County Hospital in Guildford is the only hospital in the country to charge more to park than NGH at 34 an hour.
Northampton's main hospital raked in a total of £1.67 million during the 2016/17 financial year in charges alone.
The news comes just three years after health secretary Jeremy Hunt ordered a crackdown on hospital parking tariffs, described by some critics as a tax on the seriously ill.
But an NGH spokeswoman sought to justify the charges today.
A statement from the hospital reads: "Parking revenue avoids money being taken out of patient care budgets to help cover the costs of providing and maintaining our car parks, our CCTV network and security services. Any surplus is invested in health provision.
"Parking is free for patients receiving long-term cancer treatment as well as for registered disabled blue badge holders in pay and display car parks and marked disabled bays."
The Mail Online's study revealed that hospitals made a record £175 million in parking charges last year.
They also made nearly £1 million from parking fines, an increase of more than a third on the previous year.
NGH is among only 14 hospitals across the country to charge at least £3 an hour.
Northampton South Labour parliamentary candidate Kevin McKeever said the high tariffs could be traced back to Government austerity measures.
He said: "The reason the trust has to tax ill people and their families is because of the Government's real terms cuts to NHS funding.
"This is yet another example of the hidden effects of Tory austerity."