Clare County Council increased its activity against suspected "rogue" developers by more than 30 per cent last year.
According to director for planning Bernadette Kinsella, the enforcement unit took 311 actions, a rise of 31 per cent on the 236 in 2004.
Figures published yesterday show that the council's enforcement unit served 168 warning letters and 115 enforcement notices and instituted 28 separate legal proceedings last year.
One of the cases resulted in west Clare businessman Oliver Marrinan being sentenced to three months in prison last September for failing to comply with a court order which required him to remove an unauthorised oil depot at Moyasta in west Clare.
Marrinan is on bail pending his appeal to the Circuit Court, and this week An Bord Pleanála refused him retrospective planning permission for the oil depot.
Marrinan declined to comment on the appeal outcome.
Ms Kinsella also revealed that a number of homes in Clare had to be partly demolished last year as a result of enforcement action against people who had built without planning permission.
She said: "Through the actions of the enforcement unit, the council is aware that some people still think it best to build first and think about planning later.
"This leads to a greater cost to all: a cost to neighbours or those affected by a development; cost to the person of having to regularise or demolish the development and pay the costs of the council and legal costs if the matter goes to court."
Ms Kinsella said it was vitally important that before any work started on any site the need for planning permission be considered and that where a person had planning permission it was strictly complied with.
She added: "During 2005 the council continued to take a very active role in the area of enforcement.
"Over 200 new cases came to the attention of the enforcement unit, many of which are still under investigation.
"Legal proceedings were commenced in 28 cases, with a number of convictions secured, while some cases have been finalised, with convictions and fines imposed.
"Many of the cases taken are still ongoing, and some have been appealed to higher courts and are awaiting hearing."
Ms Kinsella said that the planning enforcement unit "has striven to detect unauthorised development, respond to complaints from members of the public and statutory organisations in relation to unauthorised development and take the necessary action."
