The health secretary has written to the company that manages a hospital car park in Glasgow urging them to stop "pursuing" staff over parking debts.
Jeane Freeman sent the letter to APCOA, which runs the car park at Glasgow Royal Infirmary.
It comes after some staff racked up thousands of pounds in charges after being refused reduced cost permits.
The union Unison said the move was "extreme and immoral". APCOA said its priority was "safety".
Earlier this month it emerged that nurses had set up an online petition to rally support against an increase in parking charges at the site, which is owned by an asset management company but run and managed by APCOA.
The car park is one of three in Scotland that charges visitors and staff for parking.
Between 08:00 and 18:00 Monday to Saturday an hour's stay costs £1.70. After 18:00 through to 08:00 the next day it is £1.60 for the first hour and £1.60 thereafter. Advance tickets can be bought and permits costing £100 per month are also available.
The hospital car park was constructed as part of a long-term private finance initiative (PFI) contract, signed in 2005 under a Labour government, and which is due to last until 2035.
Charging for parking at most other NHS car parks in Scotland was scrapped in 2008.
Edinburgh's Royal Infirmary and Ninewells in Dundee, which were also constructed under PFI deals, are the only others to charge for parking.
Some staff at Glasgow Royal say they have been unable to obtain the parking permits that would entitle them to a discounted rate.
The permits are issued by the health board, which will not sanction a permit unless employees match certain criteria.
One NHS staff member, who wanted to remain anonymous, said this exact scenario had played out when he applied. He said he was never given a reason why he was refused a permit.
He said he could not afford the £20-per-day fee and had also incurred charges totalling thousands of pounds.
He added: "APCOA pass your information from one debt collector company to another, increasing the fees each time and it's now £130 a ticket.
"I now get letters asking for £2,500 in the post every few weeks, and many of my colleagues owe much more.
"The letters they send quote other cases where NHS staff members have been taken to court and made to pay thousands, to threaten you to pay up.
"It really makes going to work intolerable and it's a stress that's not needed. All we want to do is go to work and do our jobs."
An APCOA spokesman said its priority was "ensuring there is a safe environment for all our customers".
He added: "Where a parking offence occurs, a parking charge notice is issued to ensure a safe environment is maintained for all motorists."
A Scottish government spokeswoman said: "The health secretary has written to APCOA to urge them to reconsider their policy of pursuing NHS staff over these matters, and also the increased charges which have been added to the original fines."
A spokesman for NHS Greater Glasgow and Clyde said it had only become aware its staff were being sent debt recovery letters in September.
The BBC understands that the car park has been owned by a number of companies since the original PFI contract was signed in 2005.
Those companies include Impreglio and Semperian. The latest firm to take ownership, according to the health board, is Imagile.
The health board said: "As the car park is privately owned we do not have full control over the tariffs that Imagile choose to charge. However, our agreement with them sets out certain limits for them to work within."
It added: "We subsidise 941 parking permits for staff who are required to bring their car to work as they work across a number of sites.
"We were informed that APCOA was issuing debt recovery letters in September. However, we were not told who these were being issued to due to data protection issues."
Unison's head of health for Scotland, Matt McLaughlin, described the parking charge notices as extreme but said the situation was not unique.
He explained: "Private firms shouldn't be raking in huge profits at the expense of NHS staff who have no other option but to fork out and use hospital car parks.
"The government must intervene and put an end to these immoral and sky-high parking charges."
The BBC contacted Imagile for a comment but is yet to receive one.