NHS Lothian has been being warned it risks losing key workers after revoking staff parking permits at the Royal Infirmary of Edinburgh.
The much-delayed new Royal Hospital for Children and Young People will open on the Little France site in July.
It will bring the number of staff at the hospital campus to about 10,000.
But plans for the £150m facility have not included further provision for parking, leading to fears of lack of spaces for staff and visitors.
The Royal Infirmary of Edinburgh (RIE) was built under a PFI arrangement and fully opened in 2003.
When parking charges were abolished at Scottish hospital sites in 2008, they remained in place at the RIE because the car park was operated by a private contractor.
However, some hospital staff were able to claim a parking permit, which costs about £250 a year.
BBC Scotland's The Nine has learned that many people who have been able to renew their parking permits for years are now being told they no longer qualify.
They have been given three months' notice of the end of their permits, coinciding with the arrival of the new children's hospital and the Department of Clinical Neurosciences (DCN).
Neonatal nurse Sharon Johnstone has worked at the RIE since 2007 and has had a staff permit for most of that time.
She said that, in the past few weeks, staff had started to receive emails telling them their permits were being revoked.
"We haven't been given an outright reason but we believe it is to free up spaces for the new sick children's hospital which is relocating in July," she told BBC Scotland.
Staff are being encouraged to use public transport to the hospital.
Those who drive will have to pay £7.20 a day if they can find a space at the hospital car park or they will have to park off-site and walk in.
Ms Johnstone said staff were concerned over the safety of parking off-site as there had been two sexual assaults in the immediate area of the hospital in recent months.
She said she lived 30 miles away from work so driving was the only option and it was the same for many of her colleagues.
"We are all concerned about if we are going to be able to get parking spaces," she said.
"There is a park and ride near the hospital but we don't think the capacity is going to be great enough."
Ms Johnstone said she was also concerned about the safety of finishing her shift at 20:30.
"I would then be standing in the dark trying to get buses to an unmanned park and ride," she said.
Ms Johnstone said the lack of parking had been a blow to staff morale and could result in people looking for work elsewhere.
"Personally I love my job but it might make me consider my options," she said.
"It'll depend on how it hits the finances when it finally happens."
Tom Waterson, chairperson of Unison's Scottish health committee, said the issue of car parking went back to the site fully opening in 2003.
He said union members were telling him that they would be looking to move elsewhere.
Mr Waterson said the health board had its "hands tied" by City of Edinburgh Council's green transport policy of not allowing any more car parking onsite.
He said the union had been trying since 2003 to ensure there were extra car parking spaces but they were "coming up against a brick wall".
Jim Crombie, deputy chief executive of NHS Lothian, said there were a "restricted" number of car parking spaces allowed on the site because of local authority planning regulations.
He said there were 1,125 staff car parking spaces on the RIE site, which included the allowance for the new children's hospital and DCN.
There are 614 public car parking spaces on the RIE site and this will increase to 948.
Mr Crombie also said that the health board did not operate the car park and had no control over its charges.
He said NHS Lothian recently conducted a review of car parking.
"This has resulted in a car parking permit allocation process based on a points system that is fair and equitable to all members of staff applying for a parking permit," he said.