A cancer charity is stepping up its campaign for free transport and parking costs for cancer patients.
Patients can be charged up to £30 a day for parking
Macmillan Cancer Relief says many patients are paying a "stealth tax" and have to chose between finding money for hospital travel and basic necessities.
Cancer patients make around 60 hospital visits for their treatment, and many are charged up to £30 for a day's parking, the charity said.
The Department of Health said the most needy patients got help with costs.
Patients entitled to help with hospital travel/parking
Those on income support
Those on working tax credit or child tax credit
Most on pension credit
Dependents in a family on any of above
Medical escorts for patients on any of above
For its report, Free at the Point of Delivery?, the charity surveyed the 292 hospitals with cancer centres across the UK.
It found three out of four were making money by charging patients for parking.
And staff in only one in five said they promoted a scheme which allowed some cancer patients to claim this money back.
Patients are paying an average of £380 a year on travel, and costs are increasing as cancer services become increasingly centralised leading patients to have to make longer journeys to hospital, the charity added.
Macmillan argues that cancer patients are a special case because of the frequency of visits they have to make to hospital to see specialists, obtain chemotherapy and radiotherapy treatment.
Most of these will be too ill to use public transport, the charity says.
A spokeswoman said some patients would be going every day over the course of six weeks of chemotherapy.
She said the the NHS is actually saving £200 per patient per day by not seeing cancer patients as in-patients.
"But now they are pushing the costs of that on to patients.
"You may get your treatment for free but you are still paying for parking and travel," the Macmillan spokeswoman added.
Patients on income support and other benefits such as Disability Living Allowance are eligible to reclaim travel costs through the Hospital Travel Costs Scheme.
But the charity's research suggested only a handful were promoting this to patients.
Charity chief executive Peter Cardy said: "It is outrageous that patients should have the added stress of trying to find money for travel for their life-saving treatment, as if having cancer isn't stressful enough.
"That's why Macmillan is calling on the government to allow all cancer patients to get help with their travel costs."
A Department of Health spokesman said charges helped hospitals as they discourage people who are not using the hospital from using the car parking spaces.
"This can be a problem, especially in inner city areas. Most hospitals have exemptions from charges for patients, and hospital staff are generally well trained in advising patients about these exemptions.
"Many patients are eligible for free transport, either under the Hospital Travel Costs Scheme (for patients on low incomes) or through hospital Patient Transport Services, for patients requiring transport on the basis of a medical assessment, such as older or vulnerable people.
"Ultimately, it is a matter for individual NHS trusts to decide whether or not to charge for car parking, and the level of charges in the light of local circumstances," he added.