EirGrid has admitted site works began on the construction of pylons for the Laois-Kilkenny reinforcement project before proper notification was given to the authorities.
Planning permission for the pylons was granted by An Bord Pleanála after an oral hearing last year but, under the conditions set down, the company should have notified residents in the area and other agencies before work commenced.
Laois County Council, acting on a complaint about the work starting in April, is now investigating the breach in the conditions.
In a statement today EirGrid said that "as part of the approval, ESB Networks, as project developer, is required to agree certain details with the planning authority prior to the start of the development".
"Unfortunately, ESB Networks commenced early site works in April 2017 on a site in Coolnabacky in Laois prior to the discharging of these conditions. These works are approved by An Bord Pleanála.
"When the situation came to the attention of EirGrid, instructions were issued for all works to cease.
"Furthermore, EirGrid has instructed that no works shall take place until the planning conditions have been discharged."