Staff and patients at Ninewells face climbing up to eight flights of stairs because operators have switched off the lifts.
A number of complaints have been made by motorists at the multi-storey car park who have had to climb the steps after 10pm because the lift systems are being stopped.
Indigo, the company responsible for managing the site — one of only three in the country still charging users — said they do not staff the building after 10pm, meaning that the devices are switched off and unusable.
It is understood the changes came into effect last week.
Shelagh Wilson, a theatre nurse in the hospital’s anaesthetic department, was faced with an eight-floor climb after finishing a gruelling 12-hour shift.
Mrs Wilson said she attempted to get in a lift at 9.50pm, having had to park on the uppermost floor earlier in the day because of limited available space, to be told by employees they had been turned off for the night.
She said: “It can take as long as half an hour some days to find a space, so very often those of us whose shifts start at lunchtime can only find space on the upper floors.
”It’s a safety and an accessibility issue, staff who work very hard or are on call will now face having to climb a lot of stairs late at night.
”Also, some visitors might be seeing relatives in hospital later on in the evening and may themselves not be all that mobile.
“They have staff who can go out and ticket cars at all times of the day, so why can’t they keep the lifts on?
”It’s completely unfair and not right. It is entirely unacceptable.”
The car park costs users — including all staff and patients — £2.20 per visit and has been dubbed a “tax on the sick” by politicians.
The Scottish Government, which scrapped charges at sites across the country, insists it has no power to renegotiate the contract.
A spokesperson for Indigo did not comment on Mrs Wilson’s complaint, but did confirm because of the car park being unmanned, the lifts are turned off in the evening after 10pm.