Two DUP Ministers at Stormont are facing opposition following their indication of support for a private developer who wants to build a new visitor centre at the Giant's Causeway.
If approved, this would replace a plan for a publicly-funded centre at the world heritage site.
The Giant's Causeway attracts over 500,000 visitors a year. The need for a new tourist centre arose when a previous building was destroyed in a fire seven years ago.
The British government announced an international architectural competition for a replacement. The winning design costing £21m was chosen nearly two years ago.
Sinn Fein and the SDLP are raising their concerns in a debate at the Assembly this evening over what they say is a U-turn by the Environment Department.
Meanwhile the National Trust, which owns and provides access to the Causeway, claimed any development on previously undeveloped land could put at risk the area's status as a world heritage site.