Under the Town Planning Ordinance, no person shall undertake or continue a development in a development permission area (DPA) unless the development was in existence before gazettal of the relevant Interim DPA or DPA plans, or is permitted under the DPA plan or the replacement OZP, or has obtained permission from the Town Planning Board. Development not satisfying these criteria is an 'unauthorised development' (UD) subject to enforcement and prosecution action. Currently, about 19 764 hectares of land in the rural area are covered by DPA plans or the replacement OZPs.

The Planning Authority may serve statutory notices on the respective landowners, occupiers and/or responsible persons, requiring them to discontinue the UD by a specified date unless planning permission for the development is obtained, or to reinstate the land. It is an offence in law for non-compliance with the requirements of the notices.

In 2004, 280 new UDs were detected in the rural areas. Most were related to uses such as open storage of vehicles, containers and construction machinery/materials; workshops; and container vehicle trailer parks. The Director of Planning issued 1 303 warning letters for 277 cases, 1 100 enforcement notices for 164 cases, and 667 compliance notices for 113 cases. As for prosecution, 19 defendants in 12 cases were convicted. The average fine imposed was $30,419, with a range of $1,856 to $102,000. During the year, enforcement action had resulted in the discontinuation of 179 UDs covering 39 hectares of land, and regularisation of another 104 UDs covering 49 hectares of land through the planning application system.