Some 90% of homes in Rent Pressure Zones across the country have failed to meet minimum housing standards.
Figures supplied to The Sunday Business Post by local authorities with RPZs show that 16,441private rental properties were inspected last year.
There has been a significant increase in the number of private rental homes being inspected by local councils, with 58% more homes investigated in 2018 than in the previous year
The worst offenders were rental homes in Limerick City and County Council, Galway County Council and Louth County Council.
None of the private rentals inspected passed the minimum housing standards.
Home in Wicklow fared the best - of 588 homes to come under scrutiny, 56% met the standards.
Dublin City Council inspected the most properties, 3,561, of which more than 95% failed.
Minimum standards require landlords to meet requirements such as structural repair, sanitation, heating, light, safety of gas and electrical supplies and absence of damp and rot.
It comes after new zones were introduced in 19 areas across 11 counties.
This includes all of Co Meath, Co Louth and Limerick's metropolitan area.
A RPZ is a designated area where rents cannot be increased by more than 4% per year.
This applies to new and existing tenancies, unless an exemption is being applied.