The Irish Examiner obtained the pictures recently, which show the dilapidated state of Vernon Mount.
The county council, concerned about the state of the house, recently contacted the agent responsible for running it for its owner, American-based millionaire Jonathon Ross.
However, the agent turned up to meet council officials without a key and then couldn’t find one.
County manager, Maurice Moloney, said he “expected better.”
The house was constructed by Sir Henry Hayes in the 1780s and the Irish Georgian Society (IGS) describe it as one of the finest surviving Georgian villas built around Cork.
Donough Cahill, deputy director of the IGS said the building is of national importance.
Apart from the involvement of the Munster Motorcycle and Car Club, who used it for a period as their club house, the house has lain largely unused for many years.
In a letter to the council, Mr Cahill said: “The great circular fanlight over the front door was damaged in an attempted break-in, many window panes have been smashed, roof slates are loose or missing, the guttering is in a deplorable state— leading to concern about water ingress. With little or no maintenance occurring, water penetration is placing the house and its paintings at very significant risk.”
Mr Cahill added that, as Mount Vernon is recorded as a protected structure, the council should first make it weather-proof and then ensure it finds a suitable new use, in public or private ownership.
However, a number of councillors, including Cllr Deirdre Forde want the building restored for the people of Cork.
The owner until the end of this month to let the council view the interior of the house, or it will take him to court under the Derelict Sites Act.