The Rock of Cashel, one of Ireland's most iconic tourist sites, is at risk of being irrevocably damaged under proposals currently being considered by South Tipperary County Council, according to campaigners.

The plans, which they say would lead to the unnecessary rezoning of hundreds of acres of valuable land close to the rock, have prompted the national trust, An Taisce, to called on the Minister for the Environment, John Gormley, to directly intervene.

Local business leaders also fear that if approved, the proposals could put an end to hopes that the rock can be designated a Unesco world heritage site (WHS), a development which is seen as key to attracting tourism revenue to the town. The council has strongly refuted these claims.

In a letter sent to Gormley last month, An Taisce heritage officer Ian Lumley criticised the overall plan's provision for "excessive residential rezoning" in the town, including over 100 acres of newly zoned "industrial" land, and more than 140 acres of newly zoned residential land.

He claimed that there are already more than 250 unoccupied housing units in Cashel, and said there will be a "substantial uplift" in value when lands to the north of the rock is rezoned.

This could lead to "inappropriate" development applications, he said.

He also expressed concern about the risk of extending "suburban sprawl" around the eastern side of the rock, and the removal of a number of protected structures from the plans.

Dr Niall Gregory, president of Cashel Chamber of Commerce, told the Sunday Tribune that the proposals could sound the "death knell" for hopes that the rock can be designated a Unesco world heritage site.

Such a designation – there are only two such sites in the state, Skellig Michael and the Bend of the Boyne – is seen as key to boosting tourist numbers in the town. It is estimated that some 250,000 tourists visit the rock each year.

Dr Gregory, an archaeology consultant, noted that the plans allowed for twice the growth in population of the town envisaged in the 2006 census by 2020.

He also cited concerns about the erosion of an existing architectural conservation area beside rock.

"This erodes protection of the area from development and thus protection of the buffer zone surrounding the rock for inscription to Unesco world heritage status," he said.

"New residential zoning within the visual buffer for the rock…will eliminate inscription for world heritage status for the rock. There should be no residential zoning here."

However, Sonja Reidy, senior executive planner with the council, defended the plans, which she stressed were still under discussion.

"Cashel is a living and breathing town, and it needs to grow and adapt," she said. "We would see that certain sites close to the rock could be appropriate for residential use… any development would have to have regard to the impact on the visual amenity of the rock."

She said the council had been working with Gormley's department and other agencies to advance the prospects of the rock gaining WHS status.

"It would certainly be our opinion that the ethos behind the draft plan would benefit the rock, in terms of the tourism impact and accessibility. We don't feel it would in any way play a negative role."