The huge "NO" sign erected on Ben Bulben by anti-abortion campaigners is the subject of a legal complaint submitted to Sligo County Council by An Taisce.
The charity, which works to preserve and protect Ireland's natural and built heritage, says the advertisement requires planning permission.
President of Sligo Chamber of Commerce, Fiona Candon, says she is unhappy at the use of Ben Bulben as a billboard but there is unlikely to be a negative impact on trade or tourism.
She said: "It has certainly put a spotlight on Sligo and for anybody who didn't know this spectacular mountain, they certainly know about it now but we wouldn't normally advertise Sligo in this way."
The 100-foot sign, which is made out of plastic cladding, was placed on the North facing side of the mountain with the landowner's permission yesterday morning.
According to Ocean FM presenter, Naill Delaney, political messages have been previously placed on the mountain over the years.
During The Troubles in the 1970s and 80s messages such as ‘H Blocks’ and ‘Brits out’ were spotted.
- Digital Desk