CITY planners have demanded that Siptu justify why they want to demolish Liberty Hall in favour of a taller skyscraper.
In a fresh blow to plans to knock down the famous city tower, authorities say that concerns raised by the Department of the Environment will have to be addressed.
The department had said Siptu's proposal for the building could jeopardise Dublin's designation as a World Heritage Site. It added Liberty Hall "may be of special interest".
In a request for additional information, Dublin City Council has asked for "a more detailed and comprehensive analysis of the architectural heritage and contribution" of the Eden Quay skyscraper.
The building is the subject of a planning application by Siptu which, if granted, will see it demolished and replaced by a taller building.
Making an observation to the council, the Environment Department said it was "concerned" about the height of the proposed new building.
Department official Emmet Deegan, who made the submission, said, if approved, it may set a precedent for other high-rise applications in the "historic core of Dublin city".
He stated it is unclear from the department's perspective whether the proposal "accords with the policies and objectives" of the council's current and draft city development plans.
"It is our opinion that the applicant has not provided sufficient justification in the submission for the increase in height of 28m over the height of the existing building," Mr Deegan added. The department noted a policy of the draft development plan was "to support the designation of Dublin as a World Heritage Site".
He said: "The authority should consider whether or not a grant of permission for high-rise development within the historic core of Dublin city might compromise the city's authenticity and integrity in the context of any proposed inscription of the city as a World Heritage Site by Unesco."