Planning permission for an underground gold mine near Tyndrum should be refused, a chief planning officer has recommended.
Scotgold Resources is hoping to redevelop the Cononish Mine, which was abandoned in 1997.
But Gordon Watson, director of planning at the Loch Lomond National Park, said there were concerns over the long term impact on the landscape.
The application will be considered by the park authority board on 18 August.
Mr Watson said fluctuating gold prices made the predicted economic benefit of the mine uncertain.
He also said the proposal went against the aims of the National Park designation, which state that conservation should be given priority when considering planning applications.
The impact would be significant both during the 10-year proposed life of the mine and in the long term, he added.
Scotgold Resources want to mine gold and silver at the facility and also plan to build a large processing building on the surface.
The complex would cover about 39 hectares (2.5 acres) on the surface, the national park said.
Scotgold Resources will be able to put its case to the national park board at the meeting later this month, along with supporters and objectors to the project.
The company, which bought the mine in 2007, first applied for approval from Loch Lomond National Park Authority more than a year ago.
Scotgold Resources chief executive Chris Sangster said he was "very disappointed" at the decision.
He added: "We spent a lot of time, effort and money with the assistance of the planning authority and other authorities.
"We disagree with their reasons for refusal and strongly refute them."
Mr Sangster said he believed the application did not go against the aims of the national park.
Scotgold Resources' parent company is Australian and has ploughed millions of dollars into the venture.
The site is known as a gold deposit but has never been commercially mined.
Earlier this year, the company floated on the London stock market and raised more than £700,000 towards the mine's development.