The liquor licence for Ashford Castle Hotel, in Cong, will be opposed by the Consumers' Association of Ireland unless its public bar has a more open policy towards non-resident visitors.
Ashford Castle Hotel, located on the border of counties Mayo and Galway, is one of Ireland's bestknown hotels. Guests have included President Ronald Reagan.
Mr Michael Kilcoyne, chairman of the Consumers' Association of Ireland, said: "The management of Ashford Castle Hotel is acting illegally, in my opinion, in refusing to serve drinks at the castle's public bar to anyone who is not a resident of the hotel."
He said he had received "a sizeable number of complaints" from the public who had paid €5 each to enter the grounds of Ashford Castle and who had then been refused service in the castle's public bar.
"The hotel is a public place, covered under the hotel Acts and if you hold a public licence, then members of the public are entitled to go in and be served."
Mr Kilcoyne received legal advice on the matter and said if the hotel decides not to serve members of the public because they are non-residents "then it is breaching its liquor licence".
The manager of Ashford Castle, Mr Niall Rochford, said there is limited space in the castle's public bar, particularly when the hotel is full with guests. At times, non-residents are offered an alternative bar and restaurant on the grounds of the castle.
"Guests who pay an exclusive price to experience an exclusive product here at Ashford Castle are our main priority."
Residents expect not to queue or wait for service and "there is limited space in the public bar when the hotel's 83 bedrooms are occupied", Mr Rochford said.
When this is the case, visitors who have paid money to enter the castle grounds are "always offered an alternative".
He said they can avail of bar and restaurant services at the Thatch Cottage, located on the grounds, close to the castle.
"When the castle is not full of residents, than the general public are served in the castle's public bar," he said.