Denbighshire County Council is warning property landlords that it will take court action against those who fail to maintain their properties and not license them as a House in Multiple Occupation (HMO).
The warning follows two recent successful prosecutions brought by the council.
In one case, a landlord was served with an Improvement Notice under the Housing Act 2004, for his property in Rhyl.
The notice included works to be carried out to resolve complex dampness issues, being rising damp, condensation and penetrating dampness, electrical repairs, insulation and repairs to the rear door.
Following numerous emails and communication with the tenants, the council concluded that no works had been carried out to remedy the problems.
At Llandudno Magistrates Court, the landlord pleaded guilty to the offence of non-compliance and he was fined £200, with costs of £400.
In the second case, two co-owners of a property were fined for offences under the Housing Act. One was fined £2,250 for two offences, the other fined £1,500.
Councillor David Smith, Cabinet Lead Member for Public Protection, said: "Although the fine is disappointing and is a matter for the courts, it is again an important conviction for us and sends a message out to other negligent landlords that if they have an improvement notice served on them to require works to be completed, we will prosecute them if they choose to ignore it.
"The majority of landlords are responsible and take the health and safety of their tenants seriously, but not maintaining their properties properly simply will not be tolerated. The Council is there to provide advice and information for landlords and is offered with a view to landlords protecting the welfare of tenants, but ignoring that advice and guidance could result in action being taken against the landlords.
"I must commend the housing enforcement staff responsible for bringing these matters to the courts for their due diligence and perserverance in their efforts to protect the welfare of tenants."
Denbighshire County Council says it supports landlords and tenants through providing advice, responding to complaints, arranging landlord forums twice a year and producing information newsletters.