Merchants Quay Ireland has said it will lodge an appeal over the rejection of planning permission for a supervised injection facility.
The charity had applied to operate the country's first supervised facility in Dublin city centre.
However, last month Dublin City Council refused planning permission - saying there was an "over-concentration of social support services in the Dublin 8 area", and also citing a potential impact on tourism.
The decision proved controversial, with Catherine Byrne, minister of state for drugs strategy, suggesting "we've let down the most vulnerable people in society".
Today, Merchants Quay confirmed plans to lodge an appeal with An Bord Pleanála.
The group said: "Two out of every three injecting deaths in Ireland occur in Dublin city.
"These fatalities are more than statistics - they are the tragic loss of someone's brother, mother, neighbour or friend.
"We have a duty as a society to protect our most marginalised and vulnerable citizens."
It had originally been hoped that the country's first supervised injecting facility would be in operation by the end of 2017.
However, it faced a series of delays after the Oireachtas approved the necessary legislation in May 2017.
