Up to 93% of properties available for rent in August were too expensive for those on rent supplement, according to the Simon Community.
They examined the rental market areas and found just 64 properties were affordable for those receiving housing assistance.
In particular, single people were being priced out of the market.
National spokesperson for Simon, Niamh Randall, said: "We looked at 11 areas around Ireland and in the three days of the study there were 859 properties available, but only 64 of those, just 7%, were available to those within rent supplement limits.
"We looked at limits for a single person, for a couple, for a couple with one child, for a single person with one child and for a couple or single person with two children.
"So it's very, very stark, just 7% available for people on those limits."