Planning permission for a £100 million golf resort close to the Giant's Causeway was granted without properly consulting world heritage authorities or challenging the developer's economic pledges, a court has heard.
Stormont environment minister Alex Attwood acted irrationally and second guessed the views of Unesco when he gave the green light for the complex last year, a lawyer for the National Trust claimed in Belfast High Court.
Mr Attwood also did not have enough information to assess whether the backers of the ambitious scheme could make it fly financially or deliver on their job creation targets, the barrister said.
The Trust is taking a judicial review against the minister's decision to allow the development - which is planned for a 360 acre site around a mile from the Unesco World Heritage Site at the famous causeway stones.
The proposal envisages a championship course, 120 room five star hotel, 75 villas and conference facilities in the sand dunes at Runkerry near Bushmills.
The Trust claim any development on the dunes could have a huge environmental impact on one of Northern Ireland's top tourist attractions, destroying the habitat of many rare species.
The resort's development group, led by US-based Northern Ireland businessman Dr Alistair Hanna, claim it will boost tourism figures and create approximately 360 direct jobs and an estimated further 300 ancillary jobs through suppliers and construction.
Stewart Beattie QC, outlining the case for the National Trust, told judge Mr Justice Ronald Weatherup that Mr Attwood's actions were at odds with his claim that Unesco's view was integral to his decision.
"The minister has in this case presumed to second guess what the view of Unesco would be in coming to his decision because he has never had an engagement with Unesco," he said.
Since Mr Attwood's decision last February, the World Heritage Committee of Unesco has called for a halt to the development until a fuller assessment of its impact is undertaken.