Sinn Féin is questioning whether businessman Denis O'Brien has statutory permission for work to be carried out at Connemara Castle.
Work has started on the Ballynahinch lake and residents have raised concerns that the medieval castle and local habitat may be damaged as a result.
Senator Trevor Ó Clochartaigh said: "It is not clear whether or not the development has planning permission, whether the relevant environmental impact assessments have been done, whether the National Monuments Service & NPWS were properly informed, had given permission for works to go ahead and whether the appropriate archaeological studies had been done prior to works being undertaken.
"This island was the seat of the Conmaicne Mara and the O'Caodhla before it was taken over by the O'Flaherty in the 12th century. The Martins were granted the land in the 17th century and an extension was erected by 'Humanity' Dick Martin to facilitate a gaol in the 18th century. For the past two years the estate, including circa 500 acres, Ballynahinch Castle Hotel and the mediaeval island castle is owned by Denis O'Brien.
"Concerns have been raised since a scaffold was erected around the island castle in recent weeks and works appear to have begun on the ruins. Local historians, archaeologists and wildlife enthusiasts have expressed serious concerns about this development.
"It is not clear whether planning permission for the work is necessary, has been sought, approved and what restrictions pertain to that. Galway County Council need to clarify this immediately."
(CD/JP)
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