Mr Sweeney's controversial Causeway blueprint received a major boost earlier this month when Environment Minister Arlene Foster announced she was " of a mind" to grant it planning approval.

The row about the Minister's preliminary view deepened on Tuesday when this newspaper revealed that a key wing of Mrs Foster's department - its Environment and Heritage Service - had strongly recommended a refusal for the project.

It is now clear that EHS was not alone within official circles in taking this position.

Similar views were also expressed in 2002 by a Government body that gives advice on landscape design issues.

The Landscape Architects Branch was, at the time, part of the Department of Finance, but has since been switched into Mrs Foster's department.

In its submission to the DoE's Planning Service on Mr Sweeney's application, it expressed "significant concerns over the location of this proposal and how this relates to its effect on the surrounding indigenous landscape" .

The document highlighted the visitor facilities currently operated by Moyle Council and National Trust at the entrance to the Causeway.

Mr Sweeney's proposals involve a new 2,800 square metre centre on land he owns downhill from the existing buildings.

The Landscape Architects Branch stated: "Presumably, the applicant cannot insist that either Moyle District Council or the National Trust must remove their buildings or attendant facilities from their present location at the headland.

"With this in mind, we would object to the dissipation of development down the slope away from the existing development and would prefer that any new visitor centre should be sited at the headland."

The document is included in Planning Service's file on Mr Sweeney's five-year-old application.

The objection from DoE's Environment and Heritage Service, meanwhile, warned that the development had the potential to "markedly" devalue the visitor experience at the Causeway, Northern Ireland's number one tourist attraction.

Disclosures from the application file have heightened speculation about the advice given to the Minister by Planning Service.

It is clear from internal documents that officials were working towards a refusal position. Their verdict would have been given to the top-level DoE Planning Management Board, who in turn would have made recommendations to Mrs Foster.

The Management Board's report has not been made public and members of the Assembly Environment Committee are expected to press for its release at a meeting today.

The Stormont Enterprise Committee has been told that Government tourism officials anticipated a refusal decision. They had been working on an alternative scheme for a publicly-funded centre, but learned in late August that Mrs Foster was minded to sanction Mr Sweeney's rival plans. When asked if the previous indications from planners had been that approval was unlikely, Ciaran McGarrity from the Department of Enterprise replied: " That would be correct."