Those responsible have defended the move
A giant 'No' sign erected on Benbulben in Co Sligo has been ordered removed by the National Parks and Wildlife Service.
The sign was put up ahead of the Eighth Amendment referendum.
Local campaigners in favour of retaining the amendment began putting up the sign - which is made of plastic sheeting - at around 4.00am on Thursday morning.
A massive ‘No’ sign in the process of being erected on Ben Bulben mountain this morning as Referendum debate cranks up. Shades of ‘Brits Out’ sign in the 80’s #Together4Yes #loveboth #8thAmendment #sligo #benbulben pic.twitter.com/NZF4LtfOIj— Niall Delaney (@OceanNWT) May 17, 2018
The move has attracted criticism, with some saying the rock formation has been defaced.
Sligo County Council said on social media: "As the land where the lettering was placed is commonage, Sligo County Council has no role in this matter."
Tommy Banks, a member of the Sligo for Life No Campaign, is one of the organisers, and spoke to radio station Ocean FM from Benbulben earlier.
He defended their action - claiming it is 'a cry from the mountain' against repealing the Eighth Amendment.
He said: "There's several teenage young men here helping out - men of all ages - and women as well down getting ready tea and sandwiches.
"It's a cry from the mountain to save Ireland's babies, because no-one is listening."
He added: "We have all the permission from all the landowners."
But in a statement, the National Parks and Wildlife Service said: "The insinuation of alien materials such as this onto a special area of conservation is insensitive to its conservation status and incompatible with the habitat.
"The owners should procure its immediate removal so that Ben Bulben is returned undamaged to its natural and beloved state."
Political messages have been erected on Benbulben in the past - in the 1970s, for example, it was marked with the messages 'Brits Out' and 'H-Block'.
Additional reporting: Jack Quann