Support for a new privately-funded visitors' centre at the Giant's Causeway is likely to be challenged in court, an environmentalist has said.
The issue of a visitors' centre is controversial
Environment Minister Arlene Foster has said she is "minded" to accept a private developer's proposal.
Meanwhile, Economy Minister Nigel Dodds has dropped plans to spend £21m of public money on the centre.
But chairman of the Causeway Coast and Glen Heritage Trust Dr David Irwin said he was mystified at events.
"We went to international competition, we came up with what everyone considered the almost perfect solution to the problem," said.
"I think this decision is almost certain to provoke a judicial review. I don't know where that requirement will come, from but I will be very surprised if it doesn't come from somewhere."
On Tuesday, Ms Foster said she would make a formal decision at the earliest opportunity.
Later, Mr Dodds said his department and the Tourist Board had become involved "because key stakeholders had been unable to reach agreement".
He said his department had been involved as "a potential developer of last resort".
The Causeway attracts nearly 500,000 visitors a year. The previous visitors' centre on the site burned down in April 2000.
Renowned for its polygonal columns of layered basalt - resulting from a volcanic eruption 60 million years ago - it is the only World Heritage Site in Northern Ireland.
Ms Foster said she had visited the site and there was considerable merit to the Seaport Investments Ltd plan for a new Visitor and Study Centre at the site.
The assembly is due to debate the issue on Tuesday.