Housing charity Threshold is dealing with almost 1,800 live cases of tenancy termination.
CEO John-Mark McCafferty was speaking as the eviction ban lapsed from midnight on Friday.
He told The Anton Savage Show those numbers will rise.
"The number of people that we're working with, who'll be facing termination in their tenancy, is up to 479 this month," he said.
"We also know that there are notices of termination that will come to an end in May - over 260 right now - that will increase over time, and in June 120.
"Over the next two months that number will increase."
'These are people and families'
Mr McCafferty said the overall figure includes 'historic cases' that were put off by the eviction ban.
"What we're dealing with is a number of cases that come up over the last number of months with people worried about losing their home, but also historic cases," he said.
"[This is] where the tenancy termination was flagged by a landlord in September or October; they've been held or paused during the eviction ban.
"They now come into play - and in fact what we have is almost 1,800 live cases of termination, either that were supposed to happen before now or will happen in the future.
"When I say 'cases', these are people, these are families".
'The market is so restricted'
Mr McCafferty said these are cases where the termination notice is valid.
"Our worry is that for a large share of that 1,800, they wouldn't have anywhere else to go because the market is so restricted in terms of alternative housing apartments in the private rented sector", he said.
"Four or five years ago, prior to COVID, there were options for people in the market".
Mr McCafferty said this has changed because of the number of landlords leaving the market, coupled with the lack of supply.
"There's the lack of supply, and that's evidenced if you go on Daft or MyHome or you try and find rented accommodation," he said.
"When people have exhausted that, and even if they have long notice periods... it could be six months, nine months: that's cold comfort if you can't find anywhere," he added.
Listen back to the full segment below:
Main image: File photo of Threshold CEO John-Mark McCafferty at the launch of the charity's annual report in 2018. Picture by: Sasko Lazarov/Photocall Ireland