Staff parking charges at Grantham Hospital are set to increase by up to a third this week.
United Lincolnshire Hospitals NHS Trust will increase the charges on Friday, December 1.
Lincoln and Boston hospitals will see the same increases.
The Unison trades union says the parking charge increases have been introduced without consultation.
But the trust says it is losing money in offering staff parking and these are the first increases since 2012.
Hospital staff will see the price of a day permit rise from £1 a day to £1.20.
A series of banded payments, related to salaries, ranging from £9.58 to £20 a month will increase by around a third to £12.91 and £25.95 a month.
ULHT Director of Estates and Facilities Paul Boocock said: “These difficult times have led to difficult decisions needing to be made by our Trust Board including increases to public and staff parking.
“We appreciate that some staff may be disappointed with this news but we had to make the difficult choice to introduce these charges rather than reduce patient services.
“This increase puts prices in line with local government rate increases but still below most other trusts. Rates will still be less than £1 a working day for most staff.
“There hasn’t been an increase in charges since 2012, yet there has been an increase in the costs of running the service. Moreover, ULHT has paid the VAT for staff, and not passed this on. This means that over the last few years, ULHT has been subsidising the real cost of the Trust providing car parking service and not passing it onto staff. As we are now in financial special measures we need to address this balance.”
Corall Jenkins, regional organiser for the union UNISON, said: “ULHT have chosen to address the deficit by unilaterally introducing an increase in car parking charges for staff and patients without consultation.
“Staff have not been consulted and those staff who pay for parking through their salaries, have not been given a choice to opt out.
“Staff feel they are invisible as the trust seek to minimise the deficit.”