Health workers at a Glasgow hospital have staged a protest later over a 113% increase in parking fees.
The cost of a "14-exit" monthly permit for Glasgow Royal Infirmary's (GRI) car park has risen from £42 to £89.50.
Parking fees at most Scottish hospitals were abolished in 2009 but remained at three sites where car parks were built under the private finance initiative.
NHS Greater Glasgow and Clyde said a limited number of £25 permits were available for staff who needed cars.
The multi-storey car park, which opened in 2005, is owned by Impregilo Car Parking and managed by Apcoa under contract to the health board.
Approximately 940 subsidised permits are issued with priority given to staff such as consultants who need to travel between different sites.
Other staff can apply for these permits, but demand outstrips availability and not all applicants are successful.
The cost of a standard monthly permit for staff who need more than 14 exits over a four-week period has also risen, to £112.50.
Staff nurse Sharron Tomalon-Gallacher said the increases would be seen by many frontline healthworkers as "simply unaffordable".
She said: "GRI nursing staff provide a vital service to the people of Glasgow. It is imperative that they are able to get to work safely on time.
"Nursing shifts often start very early in the morning, meaning that for many public transport is not an option.
"Staff members who are unable to afford the increased costs may be forced to park outside the hospital grounds, potentially compromising their safety."
Hospital parking fees were abolished at the beginning of 2009 at the majority of Scottish hospitals, but were retained at GRI, Edinburgh Royal Infirmary and Ninewells Hospital in Dundee where car parks were built under PFI.
At the time, Health Secretary Nicola Sturgeon urged health boards to limit and reduce the charges until the contracts came to an end.
In September, the issue was raised in the Scottish parliament by Glasgow Kelvin MSP Sandra White.
She was told that the first minister sympathised with the staff, but the Scottish Government was bound by the terms of the PFI agreement signed by the previous Labour administration.
A spokeswoman for NHS Greater Glasgow and Clyde said: "Unfortunately, as the car park is privately-owned, we do not have any control over any tariff increases that Impregilo choose to make."
Labour MSP Paul Martin, whose constituency includes GRI, said: "These increases are completely unjustifiable and Impregilo, the company, should think again.
"Frontline health workers are being priced out of this car park and forced to look for spaces in surrounding streets which causes other problems.
"The health board should bring pressure to bear to stop these price hikes going ahead."