There were 38 properties within the discretionary rate of the Housing Assistance Payment Scheme (HAP) available to rent last month.
It is an increase of five properties since December 2023, according to the latest Simon Communities 'Locked Out of the Market' report.
The research was conducted over three days in March.
It found that 1,180 properties were available to rent at any price within the 16 areas surveyed, which was an increase of 508 properties since March last year.
In ten of the 16 areas - including Athlone, Cork city centre, Galway city, Limerick city, Sligo town, Portlaoise and Co Leitrim - there were no HAP properties to rent in the four household categories studied.
The four household categories are a single person, a couple, a couple or one parent with one child and couple or one parent with two children.
As seen in many previous 'Locked Out of the Market' reports, the supply of properties within HAP limits were predominantly in Dublin where the discretionary rate allows up to an additional 50% on the standard rate. This is limited to 35% elsewhere in the country.
Sligo had the lowest number of properties available to rent with two properties available across the three days examined in March.
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Three properties nationwide were available for a couple or a single person within standard HAP rates, these were located in Dublin city north, Dublin city south and Kildare.
Just 13 properties were available for a single person/couples through discretionary HAP rates in Cork city suburbs, Dublin city north, Dublin city south and Kildare.
For couples or parents with one child, there were no properties available within standard HAP limits. Meanwhile, 15 properties were available within discretionary HAP limits.
There were no properties available to couples or one parent households with two children through a standard HAP rate.
Just 22 properties were available within discretionary HAP limits, 15 of which overlapped with properties available to families with one child.
Studio apartments were enumerated for the first time by the Simon Communities.
While there are longstanding concerns about the viability of studio apartments as a sustainable option for people exiting homelessness, the charity has acknowledged that studios "may be suitable" for single person households where there are limited housing options.
There were 28 studio apartments available within HAP limits during the study period. Of these, 27 were located in Dublin, and one was located in Kildare.
Executive Director at the Simon Communities of Ireland Wayne Stanley welcomed Taoiseach Simon Harris's greater ambition on housing, but he said the Government needed to outline how that ambition would be delivered.
"A critical element of any successful plan, that will help to address homelessness, should include the delivery of at least 15,000 social housing homes for rent each year.
"In the short term, we need to see HAP rates increased, but this is not a long-term sustainable solution. The answer is more social and affordable housing," he said.
Mr Stanley said the last number of reports on HAP housing shows that the situation is at a "functional zero" for available accommodation.
Speaking on RTÉ's Morning Ireland, he said the private rental market is still an important part of the housing system.
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However, he said: "But what we're seeing is for those on low income, who have availability to access the half payment, they're having to top out, top up beyond what the local authority can provide them with from their own income and our concern is that those properties.
"If they can secure them, are not sustainable because of the €100, €200 even €300 a month additionally, they're having to pay they have to top up."
He added: "Anyone who's engaged with the private rental market will tell you how hard it is to find a property.
"Landlords are leaving the market. There are people who have a property, are staying in it. So we don't see the same level of churn."
Minister for Environment, Climate and Communications Eamon Ryan has said an array of solutions are needed regarding housing.
He said: "We need so many solutions.
"We need more social housing, we need more cost rental, we need more affordable purchase, we need more private rental and private purchase.
"We also need solutions like HAP which provides social housing in an individual way."
Mr Ryan said he believes the Government can "get up closer, just below 40,000 units, new houses this year".
"The key thing is that we do get the numbers or the overall numbers," he said.
Mr Ryan said he thought that this figure "is the one that's going to be the most important".
This, he said, was because people getting "house secure tenancy" through various mechanisms including HAP, cost rental or social housing was "what matters" to those involved.
"That there's a choice, that there are options available," he said.
Mr Ryan said this meant increasing numbers which, he said, "we are doing".
"It's going up from somewhere where it was at 20,000 four or five years ago, up to 33,000 last year, it will go higher again this year and that's what we need to focus on," he said.
Mary Jameson, North West Manager with Focus Ireland based in Sligo, said she was not surprised that there were just 38 properties available under HAP.
Speaking to RTÉ's News at One, Ms Jameson said many people cannot find a rental property that takes HAP or is affordable.
She said 190 people used their services between January and the end of March, which was 10% more than during the same period last year.
She said that because there were so few properties available, there was very little movement in the market, as people in private rental housing were staying put.
"It's just extremely limited ... and there's not a huge amount of allocations with the local authority," she said, adding that landlords were exiting the market.
The Irish Property Owners Association said the findings underscore the core issues confronting residential property owners and tenants alike.
"In the first instance, there is a pressing need for urgent action to address the regulatory and taxation challenges faced by landlords operating in the residential rental market," said Mary Conway, chair of the IPOA.
"Unless some meaningful action is taken the exodus of landlords will only threaten to exacerbate the housing crisis, leaving tenants with limited options while driving up rental prices."
