Save Our Landscapes, which opposes proposals by global cement company Cemex to extend Hyndford Quarry, said its research had suggested four out of five visitors would be less likely to visit the area if the quarry was built.
It has been earmarked for land in a so-called 'buffer zone' between the quarry and the Falls of Clyde.
The campaign argues that a tourist decline could affect as many as 200 local jobs, which depend on income from people visiting the Falls. Chairman Professor Mark Stephens said: "The economic case for the extension into the New Lanark Buffer Zone has always been feeble.
"The local authority has confirmed that there are plentiful supplies of sand and gravel under existing permissions.
"The quarry could operate outside the buffer zone for a decade.
"Provided Cemex plans responsibly, no one who works in the quarry need lost their job."
A South Lanarkshire Council spokeswoman said that the application would not be heard by the planning committee until Friday, November 29 at the very earliest.