A commercial visitor centre blueprint for the Giant's Causeway is hard to reconcile with official planning guidelines for the location, objectors have alleged.
North coast developer Seymour Sweeney is on the brink of securing approval for a new 2,823 square metre centre at the Causeway, housed in a grass dome.
His proposed building is some 1,000 square metres larger than premises planned under a public sector scheme that has now been shelved.
Environment Minister Arlene Foster controversially revealed earlier this month that she is "of a mind" to approve Mr Sweeney's proposals.
She has been challenged by MLAs on various aspects of this preliminary decision - including how it fits in with her department's development framework for the district.
This document, the draft Northern Area Plan, states that permission should only be granted for "exceptionally modest scale facilities" at the Causeway, which are "necessary to meet the direct needs of visitors" .
Alliance leader David Ford last night commented: "The draft plan does not give a specific size but it is hard to believe that an increase of this scale would be classed as exceptionally modest."
Mr Ford raised the concern directly with the Minister last week at a meeting of the Assembly's Environment Committee.
Mrs Foster accused him of using "pejorative terms" with the phrase "exceptionally modest".
But Mr Ford retorted: "It's not my pejorative language. It's your department's current draft policy."
The Minister said the area plan was one of the matters she took into consideration before making her announcement on Mr Sweeney's application.
"You can't expect me to tell you what weight I put on all of the matters that came before me until I have reached my final decision," she emphasised.
Mrs Foster also argued that the approach to the Causeway is spoiled by the present visitor buildings "on the headland", which are run by Moyle Council and the National Trust.
The public sector plan to provide a new centre involved premises of 1,800 square metres on the existing site. Its dimensions and location were chosen to comply with the wishes of UNESCO, the UN body responsible for the Causeway's World Heritage site status.
But the project has now been shelved by DUP Enterprise Minister Nigel Dodds.
The DoE's draft northern area plan sets out development ground rules for the Ballymoney, Coleraine, Limavady and Moyle council areas.
It has been the subject of a successful legal challenge, but currently remains a "material consideration" for planners when deciding on new applications.
The legal case against it was taken by Mr Sweeney, and involved the DoE's consultation process for the document.