The Thirlmere zipwire plan slid into yet more trouble today as hundreds of protesters gathered at the scenic Lake District reservoir.

Despite driving rain, the campaigners fighting the 1,200m-long "adventure" zipwire marched across the Thirlmere dam with banners, including one declaring: "This is a national park, not a theme park."

There were cheers and applause as a succession of campaigners delivered impassioned speeches against the proposal.

They included Douglas Chalmers, chief executive of the Friends of the Lake District, which organised the protest.

He told the gathering: "It's significant that our protest rally today is at Thirlmere, often cited as the birthplace of the worldwide conservation movement.

"It feels like the closing of a circle that we have come back here to demonstrate the weight of public feeling against the spoiling of a special place."

That view - that the proposed zipwire would spoil the area's unique, quiet, and natural character - was shared by everybody present. Award-winning Cumbrian filmmaker Terry Abraham said of Thirlmere: "It's a beautiful place.

"It might be man-made but so is much of the Lake District; what we see has been touched by the fingers of man over thousands of years.

"What's been proposed by Treetop Trek is, as Melvyn Bragg calls it, a commercial grab, in the very heart of a national park.

"What's planned here for the zip wires is utterly at odds with what a national park is about, what it's for, and why they exist.

"It's just the wrong location."

Sarah Cowan, a 28-year-old graphic designer from Cockermouth, said: "I feel that the Lake District is worth protecting. People travel to here from miles around to visit places of tranquility and calmness and wilderness.

"You can't say that for many places.

"It's worth protecting."

Gardener and arboreal consultant Abby Fowler, 39, has lived near Thirlmere for the last three years.

As she held her placard with its uncompromising message the the developer - the words "zip off" - she said she was particularly worried by the prospect of the unceasing noise from several zip wires.

"It would change the whole nature of the place," she said.

"It would be a lot busier, a lot noisier, and overall it would take away one of the things that makes this place special."

Retired Cockermouth GP Brian Herd, 83, said: "I feel very strongly about it. It's inappropriate to put this sort of thing in the middle of this beautiful part of the Lake District.

"I've no objection to people enjoying themselves. I know they have this kind of things in the Alps but the Lake District is a very small, and precious area. We don't want to see it spoiled."

Earlier this week, the Ministry of Defence voiced its opposition to the proposed zipwire saying the cables could pose a risk to low flying operations because pilots would not be able to readily identify the wires or safely avoid them.

The zipwire application has sparked fierce debate, with organisations including Friends of the Lake District charity and the Wainwright Society, along with celebrities such as TV star Caroline Quentin coming out against the plans.

Cumbria Tourism and the Lake District Park Partnership Business Task Force both backed the scheme, saying the project would boost tourism and the local economy.

Treetop Trek already has a treetop adventure and zip wire at the LDNPA’s Lake District Visitor Centre in Brockhole, and a site at Heaton Park in Manchester.

In an earlier statement, Treetop Treck managing director Mike Turner said: “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."