The ESB has been told to reduce the height of its planned new €150m headquarters if it wants the project to go ahead.
Dublin City Council has told the company it has "serious concerns" about the height and scale of the new building, and has suggested that it "review" its plans and submit additional information.
The commercial semi-state announced late last year that it intended knocking and redeveloping its 1960s Fitzwilliam Street headquarters, which was designed by architects Sam Stephenson and Arthur Gibney.
It was the subject of much controversy at the time, as it involved demolishing 16 Georgian buildings, but the planned redevelopment has also run into trouble.
In a letter, Dublin City Council outlined its concerns about the height and scale of the new building.
"Having regard to the height, scale and massing of the proposed development, in particular at the upper levels, the planning authority has serious concerns regarding the visual impact of the proposed development," it said.
"It is the opinion of the planning authority... that the development at its higher levels would be visually obtrusive as viewed from key points in the Georgian street and would have a significant and detrimental impact on the character of the Georgian city. The applicant is requested to respond to these concerns by reviewing the height and massing of the proposed development."
The scheme involves a complete redevelopment of a 1.2-hectare site at 13-30 Lower Fitzwilliam Street in Dublin, which will be between four and seven storeys in height.
The buildings include protected Georgian structures and others constructed between the 1940s and 1980s. In all, some 48,750 square metres of offices and apartments are planned, and 400 bicycle spaces .
The council is also seeking additional information on proposed chimneys, alternative locations of en-suite bathrooms, data on proposed outdoor terraces and "alternative proposals" for a widening of the public footpath.
The information must be lodged within six months.
The new building has been designed by Grafton Architects and O'Mahony Pike Architects, chosen following an international design competition. As many as 400 construction jobs will be created over a two-year construction period if approved.