The Department of Conservation has been warned that proposals to dig a tunnel or construct a monorail between Queenstown and Milford Sound could threaten the prized World Heritage status of the region.
Both multi-million dollar tourism projects cut through Te Wahipounamu, which was added to a prestigious list of World Heritage sites in 1990.
Conservation Minister Nick Smith is expected to decide this year whether the projects will be allowed to go ahead.
But a local group is lobbying Parliament to refuse access to the companies because it believed the application process was shonky and the developments would irreparably damage a region which includes the famous Routeburn track.
The Stop the Tunnel group, made up of residents from Glenorchy, found that the Department of Conservation (DOC) had not informed the United Nations Educational, Scientific and Cultural Organisation (Unesco) about the proposed Dart Tunnel and monorail - it was the lobby group which alerted Unesco to the developments.
Unesco approved the Te Wahipounamu region as a World Heritage site.
Dr Smith said yesterday that the chances of the region being stripped of its special status was "zip".
"Those that claim that a tunnel or any other visitor facilities of that sort would remove World Heritage status, in my view, are mistaken," he said.
But in a letter to DOC, Unesco said that the two developments were "likely to be considered incompatible" with the site's World Heritage status.
It said that the region's Outstanding Universal Value was dependent on human interference being peripheral.
Unesco officials said that the monorail track would run through areas of special grassland and areas which contained endangered kaka and yellowhead - two factors which were influential to the World Heritage award.
The organisation said that DOC had not provided environmental impact assessments of the tunnel and the monorail on the specific regions which earned Te Wahipounamu its special status.
"We recommend that until such as process ... is considered these projects should not be authorised to proceed further."
Stop the Tunnel member Trish Fraser also alleged that DOC had agreed to consider the tunnel application based on studies which were mostly based on information provided by the applicants Milford Dart Limited.