The Opposition today claimed construction industry "falsehoods" had been exposed following the publication of a report on vacant properties in the State and called for a national audit of these.
There are 345,000 empty houses or apartments in the State - or 17 per cent of all housing - according to the report published today by the Urban Environment Project at University College Dublin.
That figure is higher than a recent estimate by researchers at the National Institute of Regional and Spatial Analysis (Nirsa), based in NUI Maynooth, which put the figure at 302,625.
In a statement, Fine Gael housing spokesman Terence Flanagan said: "Finally, some truth has emerged about the number of vacant homes in Ireland.
"For months now, the Construction Industry Federation has been distorting the truth by claiming that there are only 40,000 vacant homes. It has been doing this in an attempt to con the public into thinking that a minimum of 10,000 new homes must be built this year to cater for demand. This falsehood has now been demolished.
"The fact that there are 345,000 vacant homes also exposes the myth that house prices have hit rock bottom as there is an enormous oversupply of homes available in the Irish property market," Mr Flanagan said.
The Fine Gael TD said the figure also highlighted the need for councils to refuse planning permission
"Despite these huge numbers of vacant housing, many local authorities are still granting permission for housing in areas where there is oversupply. All council planning departments must now get real and refuse planning applications for housing in areas where there is oversupply."
However, a spokesman for the Construction Industry Federation noted the 40,000 figure from the Irish Home Builders' Association was the number of new, unsold homes in the State and therefore did not include other categories such as second homes.
Labour Party spokesman on housing Ciarán Lynch said the UCD figure was a hangover from the boom years "when tracts of land were being rezoned hand over fist. He noted that while not all of these properties are immediately available for occupation, over 170,000 are, according to the report.
"Housing minister Michael Finneran must now order a comprehensive audit of our surplus housing stock, so that we can get an assessment of the viability of the various properties," he said.
The Labour TD said the report highlighted the need for a national register of house prices. "For a market to function properly, buyers need to have access to accurate information on prices, and a national database on house prices would be the most effective way of bridging that information deficit."
CIF director general Tom Parlon has said his organisation would be asking the Minister for Housing and Local Services to address areas of uncertainty and inconsistency arising from the lack of firm housing market and house building data, including the vacancy rate and level of residential construction at any given time.
Last month, the CIF also called for the establishment of a register of house prices following the cancellation of the monthly ESRI/Permanent TSB House Price Index.
The Department of the Environment estimates there are between 122,000 and 147,000 empty homes, although these figures exclude abandoned homes, which the 300,000-plus figure from the Maynooth's Nirsa does not.
