Landlords may be prosecuted for demanding rent greater than the market value under new laws which came into effect yesterday.
It will also be illegal for landlords to seek a rent review within a year, unless there has been a substantial change in the nature of the accommodation.
Tenants and landlords will be able to refer complaints to a new State-funded mediation service which was officially launched yesterday.
The Private Residential Tenancies Board (PRTB) has been set up to help resolve disputes between landlords and tenants, as well as operate a national register of private landlords. It will work from a new database that will determine the typical market value for rental properties.
The dispute resolution service, meanwhile, aims to provide a speedy, non-confrontational service as an alternative to taking issues to the court level. The board has appointed mediators and adjudicators who will oversee the dispute resolution system.
The PRTB has been on a statutory footing since September and has been concentrating on compiling a list of registered landlords. Landlords who did not register by the December 1st deadline now face late registration fees or fines of up to €3,000.
While there was a slow response to the registration drive, officials yesterday said they had received 50,000 to date and more were arriving by the day. Due to a late surge in numbers seeking to register, the PRTB said phone lines were often jammed.
The Minister of State with responsibility for Housing, Mr Noel Ahern, said any landlord still seeking to register would be treated "sympathetically".
"We're not in the business of trying to penalise landlords," he said.
