Scores of ghost estates worth millions of euro are scattered across the country more than 15 years after the housing crash.

Figures from a forthcoming Department of Housing survey of all local authorities, taken between April and May last year, show that 75 ghost estates, or "unfinished developments", are still in place nationwide.

Despite a desperate housing shortage, the audit found there were 90 fully built but vacant homes, more than 500 people living in partially completed estates, and an unknown number of "shell" buildings which experts say could be redeveloped to help address the housing crisis.

Housing analyst Mel Reynolds said the Government should consider redeveloping half-built homes to tackle supply issues. "If you're looking at a house when it's completed being worth say €450,000 or €500,000, the cost of the finishing items could be about €180,000 or €200,000," he told RTÉ's News At One. "But that means, for that cost, in about ten or 12 weeks to go in and finish off a shell of a home which would look like ruins or basically ready to be flattened, you could end up with a four-bed house for €200,000.

"This should be viewed as a real opportunity by the department, to go and quantify how many of these are there, where are they located and hit this thing like a ton of bricks."

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At a national average price of €360,000, the 90 completed homes alone would be worth more than €32m, but with the partially built houses and apartments and those not even started included, the abandoned sites are worth many millions more.

However, it would take millions to bring the abandoned sites back into use and ensure the water, gas and electricity supplies are connected and working.

The 75 ghost estates include 40 entirely unoccupied estates and 35 partially occupied estates. The empty estates exist despite a target of 33,000 new homes needed annually.

Of the 35 partially occupied estates, 22 are entirely occupied but are still classed as unfinished because of problems with roads, green areas and water or electricity connections, while the remaining 13 of the partially occupied estates include 43 vacant but fully built homes, figures obtained by RTÉ from the Department of Housing show. More than 500 households live in partially occupied ghost estates, including 459 households living in houses and 63 in apartments.

In a statement, a Department of Housing spokesperson said the ghost estates figure is down significantly compared to 2010, when there were almost 3,000 unfinished developments nationwide, accounting for more than 70,000 homes.