The State has been accused of failing in its duty to protect Tyrone House, an 18th-century building in south Galway.
The listed building's remaining artefacts are being pilfered on a continuous basis, according to Mr Gordon St George Mark, a descendant of the St George family, which originally owned the mansion.
"This is the fate that could meet Lissadell House in Sligo, if the State doesn't recognise the value of these properties," Mr St George Mark said.
Tyrone House, which overlooks the Clarenbridge oyster beds of south Galway, inspired Somerville and Ross's The Big House of Inver, and the St George family mausoleum was immortalised in Sir John Betjeman's poem, Ireland With Emily. It was designed for Christopher French St George by John Roberts, the 18th-century Co Waterford architect who was also responsible for Mayo's Moore Hall.
The house was abandoned in 1905, and was torched by the IRA during the War of Independence in 1920. An elderly and bed-bound caretaker was reputed to be in the house at the time, but the IRA carried his bed, bedding and furniture downstairs, put him in one of the out-offices and then set the place alight The building has been the subject of continuous looting ever since.
Corner stones, original fireplaces, window frames, balustrades and other valuable architectural features have been removed from the limestone structure in recent years. Some of these were recovered during an investigation by gardaí. Galway County Council says it has attempted to purchase the building from its current owner on behalf of the national monuments section of the Department of the Environment.
"We have had reports of damage to the building, which we have investigated, but we cannot put a security guard out there full time either," Mr Tony Murphy of Galway County Council told The Irish Times.
The council says it has "not made a decision" on issuing a compulsory purchase order for the building. Mr Gordon St George Mark, who was on a recent visit to Galway, said that the sale of land for once-off housing around the property posed a further threat to the integrity of the maritime environment.
The house includes a walled garden, outhouses and a tower house, which is believed to have some archaeological significance as it predates the other buildings. The complex could be used for community and tourism purposes if acquired by the State, he says.
Mr Michael Gibbons, Connemara-based archaeologist, said that Tyrone House was of major importance architecturally and the landscape integrity of the house, gardens and adjoining harbour should be maintained.
Mr Gibbons has been involved in mapping the zone close to Tyrone House.