A quarter of housing estates thrown up during the housing boom are plagued by serious health threats, including open sewerage and water contamination.
The stark preliminary findings of a Government study of so-called ghost estates are being pored over by officials charged with clearing up the mess left by boom-time developers.
While councils will be handed the power to seize control of the worst unfinished developments, the National Assets Management Agency (Nama) will take over the lion's share.
Inspectors are visiting the sites and drawing up a detailed map of every housing estate granted planning permission in the past five years.
Planning Minister Ciaran Cuffe has ordered a full report for next month, but a pilot study of Co Laois which has just landed on his desk already suggests the scale of the fiasco. It found:
The Department of Environment expects the findings will be echoed in the countrywide survey, which will include a county-by-county breakdown, expected in September. It was initially believed developer bonds or securities would finance an overhaul of half-finished estates.
The money is supposed to be lodged with local authorities to guarantee housing estates will be properly completed.
But the survey has revealed a "maverick culture", where speculators simply ignored preconditions and pressed ahead with their plans, according to one senior official.
"While a lot of bonds were not paid at all, in other cases they were so minuscule that they are now deemed irrelevant, given the scale of the clean-up operation.
"A lot of developers didn't even pay bonds," said one Government official.
"Even in some cases where there were conditions to pay bonds, a lot of them just went ahead and started developing without discharging any of the pre-commencement conditions.
"They just went ahead and did it."
The Department of Environment believes planning permission will elapse on many of the estimated 620 ghost estates in the coming years. The agency will then have to decide whether to seek extensions if they are to be completed.