A proposal to build a major zip wire attraction over Thirlmere, in the heart of the Lake District, has been rubbished by conservation campaigners, who say it is at odds with the area's National Park status.

The scheme submitted to local planners by company Treetop Trek would see the creation of an 'activity hub', with eight zip wires up to 1200m long passing directly over Thirlmere. In addition, the proposal includes new car parking and an 18km cycle track around Thirlmere. This would all be built on land leased from United Utilities.

With a similar facility already operating at Brockholes, near Windermere, Treetop Trek are seeking to expand in the Lake District. Their proposal for a zipwire attraction at Glenridding was rejected by the Lake District National Park Authority in 2014, in the face of overwhelming local opposition.

"We have been very carefully considering locations within the Lake District for the last three to four years and are confident that Thirlmere would provide the perfect site for an exceptional family activity hub" said Mike Turner, Managing Director of Treetop Trek.

However, conservation, walking and mountaineering groups Friends of the Lake District, the BMC, the Fell and Rock Climbing Club and the Open Spaces Society are united in the opposite opinion - that Thirlmere would in fact be an immensely unsuitable location for such an attraction.

Objections range from the noise and visual impact of the zipwires, in an area generally characterised as 'unspoilt', to issues with visitor and traffic management.

Laura Fiske, planning officer at Friends of the Lake District (FLD) said:

"If approved, this application would have significant harmful impacts on the landscape and tranquillity of the Thirlmere valley. Fundamentally we consider that introducing commercial activity into this area would be at odds with the reasons for the designation of the Lake District, as it conflicts with laws and planning policies that protect the spectacular landscapes of our National Parks."

"The development would also create an unacceptable precedent – if approved it would open up the whole Lake District National Park and other national parks to inappropriate development."

The proposal runs counter to the statutory purposes of the National Park Authority, they say, which in any conflict between development and the environment is obliged to favour conservation.

"While Friends of the Lake District supports the need to strengthen the local economy with appropriate development in the right location, this is inappropriate in the open countryside" continued Laura Fiske.

"Since the establishment of the National Park, development has rightly been restricted to protect the outstanding beauty and sensitive environment of the Lake District. The right to enjoy free access to the unspoiled and spectacular landscapes is vital to Cumbria and the Lake District's tourism industry. This development would severely affect the opportunity of many visitors to peacefully enjoy the landscapes of the Thirlmere Valley and surrounding fells and should be refused."

National Parks are for everyone to enjoy, they suggest, not just for paying customers at a tourist attraction.

Public resistance to creating a reservoir at Thirlmere to service Manchester in the 1870s was a pivotal moment in the history of the conservation movement, leading to the birth of campaign groups and, eventually, to the designation of National Parks.

Ironically, the expanded lake and its wooded shoreline now form an integral part of this high quality landscape.

"That battle showed that landscapes matter to everyone" explain FLD, "not just those who own land; it highlighted the incredible natural resources of the Lake District but also their vulnerability and sensitivity. This proposal once again brings these issues into focus, albeit in a thoroughly modern context."

• The planning application can be viewed here
• Friends of the Lake District are encouraging the public to object to the zipwire proposal by writing to the planning authority - see here.

FLD have not objected to the proposed cycle route.

Informal opposition to the plan seems to have coalesced around a Facebook group, Zip Off, members of which have been busy posting comments and photos of tree felling and road works being carried out at Thirlmere by United Utilities. It is not clear whether this work is pre-empting a planning decision, or unrelated.

United Utilities have told us that their relationship with Treetop Trek simply extends to leasing them the land, in the event that planning permission is secured. The proposal and its development is entirely a matter for Treetop Trek, they say.

Treetop Trek have so far failed to respond to our invitation to comment.