The environmental group, An Taisce, has claimed the planned M6 motorway will run through the historic Battle of Aughrim site in Co Galway. It says the project will be what it calls 'particularly destructive'.
But the National Roads Authority has said the criticism is unjustified.
While a planning hearing into the motorway is ongoing, a row has erupted between heritage groups and the National Roads Authority.
The Academy for Heritage maintains the motorway routing is 'deeply alarming' and would be 'extraordinarily insensitive'.
However, the NRA says that steps have been undertaken to avoid any impact to the battle site proper - something it asserts is clear in the Environmental Impact Statement.