Car parking charges at NHS hospitals totalled £110 million last year, according to the Liberal Democrats.
He cited the £2.8m collected by Addenbrooke’s Hospital as being among the highest in the country.
He said: “No one is denying the need for hospitals to cover their costs, but that doesn’t mean they can use hidden charges to help themselves out of financial black holes.
“Ministers have ducked this issue for far too long and failed to ensure that government guidelines are actually being followed.”
Stephen Robinson, Lib Dem candidate for Chelmsford, Essex, said: “I raised the charging issue when I met Broomfield Hospital managers last year and will do so again.
“Mid Essex Hospitals must cut their ‘tax’ on patients - excessive car park charges, high bedside phone and TV charges and expensive 0844 phone numbers.
“We now need an urgent review into whether hard-working doctors and nurses and the chronically ill should be paying these charges at all.”