A quarter of housing estates thrown up in recent years are plagued by serious health threats including open sewerage and water contamination, a Government survey has found.
The stark preliminary findings of a national 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.
Official inspectors are visiting the sites and drawing up a detailed map of every housing estate granted planning permission in the last five years.
Planning Minister Ciaran Cuffe has ordered a full report for next month but a pilot study of Co Laois that has just landed on his desk already suggests the scale of the fiasco.
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 pre-conditions and pressed ahead with their plans, according to one senior official.
"A lot of developers didn't even pay bonds," said one Government official.