Renters are being hammered to the point of being pushed into poverty, according to Dr Rory Hearne.
The assistant professor in social policy at Maynooth University says this is a 'social catastrophe'.
He was reacting to new CSO figures on income and living conditions for 2020.
It found that after deducting rent paid, the risk of poverty for people renting without housing supports increased from 16.7% to 30.7%.
But the largest increases in the at-risk of poverty rate are among single adult households.
For those in households with one adult and children under-18, the poverty risk rate grew from 31.8% to 50%.
Dr Hearne says there's a growing gap.
"What really jumps out here is that renters are being hammered - and hammered to the point of being pushed into poverty.
"What we're talking about here people who's annual disposable income, what they have to spend, would be less than 14,000 a year.
"This is really people that are struggling.
"And what we're seeing is... a third of renters, who get no State support, are in poverty after they pay their rent."
And he says an extra 100,000 children are being left in poverty as a result.
"What this means in terms of children in poverty in this country, is that prior to housing costs, about 200,000 children are in poverty.
"But after housing costs, an additional 100,000 children are left in poverty - brining it to one in four children in the country are in poverty after housing costs.
"It's a social catastrophe that's going on out there for renters.
"This is really a cost of living crisis that has been building for years.
"But people can't sustain this".