Every private rental property inspected in Co Cavan last year was in breach of regulations for registered tenancies.
County Monaghan has the best compliance rate in the country, even though 55% of rental properties inspected were not compliant.
The figures come from the latest annual report by the National Oversight and Audit Commission, which measures the performance of local authorities.
Nationwide, less than 7 percent of registered rental tenancies were inspected last year.
Of those which were checked, 93 percent did not meet minimum standards.
The minimum standards require the property to be in a sound state, inside and out.
This includes ensuring roofs, windows, floors, gutters, and doors are maintained in good condition.
The landlord must also ensure that all gas, oil and electricity installations are in safe working order and that every room has adequate ventilation and both natural and artificial lighting.
All 119 dwellings inspected in Co Cavan failed to meet these standards.
This was also the case in Laois, Galway City, Waterford, Kilkenny, and Carlow.
Co Monaghan had the best compliance nationwide, even though 55 percent of the 243 rental properties inspected breached the regulations.
