British Mountaineering Council representatives were at the opening of the public inquiry into the Longstone Edge quarry in the Peak District.
Also at the hearing were former Labour deputy leader Lord Hattersley and Tory chief whip and local MP Patrick McLoughlin.
The inspector told the packed meeting at Calver Village Hall that he would be basing his decision on the legal technicalities of the 1956 planning permission under which the quarry companies were operating.
Objections were put to the inquiry by the Campaign to Protect Rural England, the Peak District National Park Authority and the Save Longstone Edge Group. Bleaklow Industries, which owns the land in question, and the quarry operators MMC Minerals then put their cases.
The inquiry is expected to last about a week.