Vandals and fireraisers have cut fencing and removed cemented building blocks as they target a listed building in Angus.
The developer behind plans to turn Strathmartine Hospital into flats has documented problems securing the site, despite increased measures.
Dozens of firefighters battled a major fire in the main building in April, which is believed to have been set deliberately.
Fire crews again reacted to a small fire within the hospital grounds last month.
However, the full extent of the problem has been revealed in a new report, calling for a speedy resolution to planning delays, which claims the situation is now “a threat to public safety”.
“Even with regular perimeter patrols, the fence is cut, repaired and cut again within a matter of hours,” the report by developer Heathfield Ltd states.
“Ladders, hammers, chisels, screwdrivers, gas canisters have all recently been found abandoned when individuals have been caught or confronted on site.
“There appears to be a threat to public safety and a real threat to the listed buildings which appear to be the main focus of attention.”
“Planning permission to convert the hospital into 24 flats and build 198 new homes in the vast grounds was granted by Angus Council towards the end of last year.
However, the decision has now been referred to the Scottish Government. Dundee City Council objected to the development near its border on the grounds that the number of new build homes was “excessive and not justifiable”.
Heathfield Ltd say the number of new homes is required to make the project financially viable.
In the report, which will be considered by the government reporter, the firm states that it is “almost certain” there will be further vandalism if the redevelopment plans aren’t given the go-ahead.
It added: “The site has remained undeveloped for some 10 years and has suffered through theft, vandalism and arson.
“There is little that realistically can be done to protect such sites and it is almost certain that further damage will be caused if the buildings are not saved.
“Any redevelopment needs to be viable, the site is large and complex and delivering redevelopment is a priority.
“If planning permission is not granted, there can be little realistic prospect of saving the listed buildings or delivering any beneficial re use of this site.”
Monifieth and Sidlaw councillorMargaret Thomson said she was aware of the vandalism problems at the site.
She said: “Initially it was put down to kids but it seems to be becoming more regular and more serious.
“I just hope we get a quick decision from the Scottish Government. Security has been increased but it’s very difficult because it’s such a huge area.”