Landlords have been ordered to retract threats to impose charges on tenants as a direct result of the Government's rent control measures.
The Irish Property Owners Association released a statement last month which suggested it would add on fees in a bid to get around new rent caps.
The country's five cities were declared 'rent pressure zones' before Christmas, after legislation was pushed through the Dáil.
However Fergal O'Leary from the Competition and Consumer Protection Commission says landlords can't go ahead with their plans: "The measures that have been put in place by the Government will continue as they are meant to do.
"What are investigation has done is stop this trade association from coming in and trying to circumvent this on a large scale across the country so it is important for comsumers.
"Consumers should benefit from this measures by the Government and our work will help with that."