Around 20 families in Dublin are at risk of losing their homes after being told the apartments they are living in never got planning permission.
A total of 45 apartments were built near Clondalkin, but the developer was only ever given approval to build 27.
South Dublin County Council has now stopped helping tenants pay their rent, and the owner of the building has given them a month to pay up or move out.
Damian Farrell, an activist with The Campaign for Public Housing, said: "The developer, owner/developer acquired what was originally a privately-operated gymnasium and a swimming pool, and he has turned it into apartments, but he's done so without acquiring the necessary planning permission," he stated.
"And as a consequence, families who have already moved in there, who are in receipt of state payments, have had those payments stopped now and at the moment they are at risk of being evicted from the property."