THE number of 'ghost' housing estates stands at 2,700 -- four times higher than thought, according to the first official government estimate.
This means that taxpayers face an even bigger bill for the mess caused by developers and the banks.
Ghost estates are defined as those that contain unfinished, unoccupied, or partially occupied house and apartment blocks.
The first government-ordered audit of how many such estates exist has now revealed the extent of the problem. A previous estimate, earlier this year, calculated there were 621.
Many of the estates in the new total of 2,700 are located in the midlands and north-west, the Irish Independent has learnt.
The report outlines six categories of properties,ranging from those which are 'turn key''-- finished but unoccupied-- to estates where only preliminary groundwork has taken place. Other estates are partially occupied, but have half-built houses and apartments which are boarded up.
One-in-four unoccupied buildings in ghost estates pose serious safety risks because sewers have been left open, water is contaminated and building sites are not secured properly.
Last April, Planning Minister Ciaran Cuffe and Housing Minister Michael Finneran jointly ordered an investigation into the scale of the problem.
Each local authority was told to report the exact number of ghost estates in their area.
As a result, a report outlining the situation is to be published in the coming weeks.
Many of the new houses will be bulldozed because of health and safety concerns. Others will be taken over by local authorities for use as social housing.
Some of the estates have been taken over by banks after developers went bust. These will be finished by other builders and sold at a discount.
It was initially believed developer bonds or securities lodged with local authorities would finance an overhaul of half-finished estates.
But in many cases developers ignored preconditions and pressed ahead. While many bonds were not paid at all, in other cases they were so small that they are now deemed irrelevant given the scale of the clean-up operation.
This means that taxpayers will have to foot the bill. Many estates will be bulldozed, others will have the houses finished and sold.
NAMA has indicated that it is prepared to demolish half-completed buildings which it believes have no value as homes.
Sources said the government audit reveals that many of the ghost estates are attached to villages and towns in the midlands and north west, with Leitrim, Sligo, Longford and Roscommon worst affected.
Taxpayers face the prospect of having to foot the bill to make the sites safe because developers failed to pay bonds that would be used to complete the developments.
The number of housing units in ghost estates is believed not to exceed 100,000.
Government sources said that following publication of the report detailing precise numbers and locations, an action plan will be put in place.
Councils will be given power to take control of the worst unfinished developments, while NAMA will take on the lion's share. The main concerns about many of them relate to water, sewerage or road access.
Planning permission will expire on many of the ghost estates in the coming years and NAMA will have to decide whether to seek extensions to allow them be completed.
Otherwise, councils will be allowed to take charge and complete unfinished roads and sewerage as well as demolish half-finished houses.
The sources said: "Some of these half finished houses are actually rotting. There are obviously very serious health and safety issues here. Some of those which are uncompleted will have to be knocked."