Housing stock needs to be replenished, especially in cities.
The latest report from Daft.ie has found the number of available rental properties is less than a quarter of what it was five years ago.
At the end of last year the average rent was close to €1,000, with values up 9% nationally.
Rent increases were higher in regional cities, with Cork seeing them jump by more than 15%.
Galway was up over 13%, and Limerick rose 12.4%.
Meanwhile, costs in Dublin only increased 8.2%- less than the national average of 9%.
Supply key
Trinity Economist Ronan Lyons compiled the Daft.ie report, and says lack of supply is the key problem:
"This is about a lack of homes. We have a growing population, but we don't have a growing housing stock - we need to get building again, particularly in the major cities.
The stumbling block around that appears to be the cost of construction.
If we can reduce the cost of construction, then we can make housing more affordable, and therefore we would see more builds."
Simon reacts
Simon's national spokesperson Niamh Randall says the latest figures are proof of a national crisis:
"People on low incomes, and those who are receiving State supports, just cannot afford the rents out there.
For the State to say to people who are trapped in emergency accommodation tonight, or sleeping rough, that there is no prospect of an affordable home anytime soon really is just unacceptable.
People need homes."