Almost 500 housing units are lying empty in Dublin, despite 44,000 people on waiting lists for homes.
New figures obtained by Fianna Fail show there were 372 vacant properties in the city alone as of last April.
Spread out across the four local authorities in Dublin, the figure rises to 492, with each council recording increased numbers over last year.
In total, there are 26 more vacant housing units in Dublin than there were in 2015.
Fianna Fail housing spokesman Barry Cowen said the number of vacant units is a major concern.
"It's unacceptable that there is still such a high number of vacant housing units owned by local authorities which are not in use," he said.
"This is at a time when social housing waiting lists are at historic highs and emergency homeless shelters are running out of space to accommodate the escalating crisis.
"The figures show that refurbishment of vacant social homes by local authorities needs to be ramped up."
Mr Cowen said the money spent on "firefighting" the homelessness crisis could have been used more efficiently had the vacant units been opened up.
"It's utterly senseless to have so many properties lying vacant while spending such enormous funds firefighting the crisis through the provision of emergency homeless accommodation," he said.
"This money could have been much more productively used to provide long-term homes for these families by refurbishing the vacant units already in the ownership of local authorities."
The figures obtained also featured every other vacant housing unit in the country, adding up to 2,751 nationwide.
The country total was down 427 on last year, indicating that the problem has had a more significant effect in Dublin.
Meanwhile, housing association Respond has opened 14 units for 14 families in a development in Lucan.
The families, which include 58 children and 20 adults, had been on the South Dublin County Council housing list, many for a considerable time.
They were welcomed to the Moy Glas Estate with a street party that included face-painting.
South Dublin Mayor Guss O'Connell said he was delighted with the warm reception the families received.
"In South Dublin we are not just about providing houses, urgent and all as that is, but even more importantly we are about building communities," Mr O'Connell said.
"The involvement of Respond here in Moy Glas Glade is to be welcomed, given their track record in this regard.
"In turn, the families are coming into a most vibrant and active community here in Moy Glas Estate."
Respond chief Ned Brennan said there is a lot more work to be done across the capital to solve the housing crisis.
"We are proud of this development and hope Moy Glas Glade will prove best-practice in terms of the quality of the housing supplied and the quality of the support services for the residents," he said.
"Housing is only the first step - real success comes from the creation of flourishing communities.
"We wish the new residents well as we continue our work of building social housing and creating communities nationwide, and we would also like to express our gratitude to the Dep- artment of Housing and South Dublin County Council."
The building of Moy Glas Glade was financed through a combination of the Capital Advance Leasing Facility (CALF) and a Payment and Availability Agreement (PAA).