Image copyright PA Image caption Seven hospital trusts earned more than £3m from charges in 2014-15

A third of hospital trusts in England have increased their car parking charges in the last year, it is being reported.

The investigation by the Press Association news agency found some are now charging £4 for a one-hour stay.

It showed most trusts did not increase their charges, but the average rise among the third that did was 15%.

The analysis combines figures obtained from NHS trusts and data submitted to statistics body NHS Digital.

The most expensive trust in the country for a one-hour stay is the Royal Surrey County Hospital in Guildford, where patients are forced to pay £4 for any stay up to two hours.

'Frequent trips'

Deputy chief executive Alf Turner said the charge was necessary to cover running costs and fund the expansion of the car park that is taking place.

"I do not like having to charge people for car parking and in an ideal world we would not have to," he added.

At the other end of the scale, car parking at Trafford General Hospital in Greater Manchester is free for up to three hours.

Some trusts allow patients and visitors to park for free for the first 30 minutes before charges start.

But others have scrapped cheaper charges for short stays, meaning people have to pay a flat fee covering up to three hours even if they are only staying for 45 minutes.

The most expensive trusts in England (for a one-hour visit)

Royal Surrey County Hospital - £4 Hereford County Hospital - £3.50 Stockport - £3.50 Bristol Royal Infirmary - £3.40 West Suffolk Hospital - £3.30

Of the 209 hospital trusts that reported figures to NHS Digital for both 2014/15 and 2015/16, a third showed an increase in their average charge for a three-hour stay.

Some 60% showed no change over the year, while 7% showed a decrease.

Some 38% also said they also charged for disabled parking.

England is the only part of the UK where hospitals routinely charge patients and visitors for parking.

Laura Keely, campaigns manager at Macmillan Cancer Support, said charges are particularly unfair on cancer patients. "They often need to make frequent trips to hospital. They should not be left out of pocket in order to receive life-saving treatment."

Some NHS trusts offer concessions to visitors whose loved one is terminally ill and also discounts or weekly tickets for lengthy courses of treatment.

Last December, figures obtained under the Freedom of Information Act by the Press Association revealed that some NHS trusts are making more than £3m a year from car parking fees.

Of more than 90 trusts that responded to the FoI request, half were making at least £1m a year.