Car park vandals could be "putting lives at risk", a hospital trust said.
Barriers at Reading's Royal Berkshire Hospital's Craven Road car park are no longer working after a series of vandalism incidents, including a 4x4 vehicle driving through one.
The damaged barriers mean people have been parking for free while staff and patients have unable to park, causing "lengthy delays" to appointments".
The Royal Berkshire NHS Foundation Trust said police are involved.
A spokeswoman said the damaged barriers meant people not using the hospital were using the car park and causing a shortage of spaces.
The hospital said in a Facebook post: "Essential staff are arriving for work and are unable to find parking spaces due to people using the car park when the barriers have been vandalised.
"This is causing lengthy delays to patient appointments - often for very serious illnesses like cancer."
The trust previously apologised after it was revealed barriers and parking meters had been working on-and-off since June.
Last year the trust raised £1.48m from parking, according to figures from NHS Digital.
A third of that comes from staff.