A new survey from the Simon Communities showed that just 41 properties were available to rent under the Housing Assistance Payment (HAP) scheme last month.
The HAP scheme is a monthly payment from the State that goes towards paying rent.
Forty of these properties fell within discretionary HAP limits, and only one was available to rent under a standard HAP rate.
This was a one-bedroom property in Co Kildare suitable for singles or couples.
The properties within HAP limits were predominantly available in Dublin, where the discretionary rate allows an additional 50% on the standard rate.
Eleven of 16 areas surveyed had no properties available to rent in any household category within standard or discretionary HAP limits.
This included Athlone, Cork city centre, Galway city centre, Co Leitrim, Limerick city centre, Sligo town and Waterford city centre.
Wayne Stanley is Executive Director at the Simon Communities of Ireland.
He said the available properties amount to almost nothing, considering the levels of homelessness.
"41 properties when spread across 16 areas - and when we think about 11,500 people experiencing homelessness and looking for a way out - what 41 properties means is essentially there's functional zero," he said.
"For people to access the properties in the private rental market now, they're really having to top up or find alternatives."
Mr Stanley said the figures are worrying as the moratorium on rental evictions will cease at the end of March.
"If we can achieve things over the next 12 weeks - if we can see allocations increasing to people in homelessness and we can see those numbers coming down," he said.
"If we can see real action on the modular build, on vacancy, on dealing with the dereliction in our towns and cities - and those brought into the public housing system - I think we'll be in a better space.
"If we're not, and we're standing still, I'd be really concerned about what's going to happen in April," he added.
The quarterly Locked Out of the Market report showed there were 757 properties available to rent at any price within 16 study areas over three dates surveyed.