The day-trippers have gone home as we look north to the dark shape of Ben Lomond, etched against orange sky, hanging over polished water.

Shadowed banks tumble down to the loch. It's dusk on a Sunday evening and we've stopped on our way home on the southern edge of the bonnie banks to stretch our legs.

It is beautiful, but it's difficult to enjoy because the beach is covered in litter: dozens of plastic bottles, takeaway wrappers and carrier bags filled with rubbish.

There are plastic plates, polythene wrappers, polystyrene coffee cups, food waste and beer bottles, all within a few metres: it seems a casual, nasty insult.

For weeks I have been trying to pry open the debate about managing visitors in the Loch Lomond And The Trossachs National Park, as the 10th anniversary of its founding approaches.

There are concerns that traditions of free-and-easy use by those living close by are being lost and ordinary people are being excluded, the park has done little for its £9 million budget, is fussy and proscriptive, and favours business and development.

But, while the critics may have a point, it's clear the park is up against a far bigger challenge than satisfying them: it has to protect a place that is a natural wonder and a destination for people happy to destroy it.

From Conic Hill looking south-west you can see the Highland Boundary Fault. The great geological crack splitting mountains to the north from lowland fields manifests itself as a straight line of islands.

The park isn't the finest Highland landscape – that might be Lochaber, Glen Coe, Torridon or the Skye Cuillin, none of them national parks – but the fault makes this place special and explains the pressures it is under.

Fewer than 15 miles away lies Glasgow and its satellite towns with a population of 1.7 million. Each year 2.2m people visit the park, spending £153.4m, and that pressure was the reason this area became a park, rather than Skye or Glen Coe: this fragile landscape needed immediate protection.

The aims of the park authority are to conserve natural and cultural heritage, promote understanding and enjoyment and boost sustainable economic development and use of resources.

Its chief executive, Fiona Logan, says she and her staff are "unashamed" in their focus on "the visitor experience" – but the most noteworthy thing the park has achieved has been to limit what visitors can do.

There's been a tradition for 100 years among outdoor enthusiasts of lighting fires by the loch and camping. But like bagpipes squalling out of car parks for tourists, a fine tradition can become a nuisance. In recent decades the eastern loch shores became, for an ugly minority, a party scene, part of the central belt's drinking culture.

Joe Twaddle and his wife Betty run a bed-and-breakfast at Balmaha on the eastern shore. Joe is secretary of the community council which covers the east side of the loch.

"Three summers on the trot we had our wooden garden furniture stolen to be used on bonfires, so we bolted it down," Betty says. "Then someone pinched our wooden flower troughs so we had to screw them down."

Their friend, John Bannerman chairs the community council. "Sallochy Bay was one of the worst blackspots," he says. "There were notorious families there for weeks at a time, drinking from dawn till dusk."

In 2005 a man was charged with attempted murder after a young female camper was run over at Sallochy Bay on the eastern loch shore – he was convicted of dangerous driving – and in 2010 a man was jailed for 14 months for a racially motivated attack on a group of Muslim campers. "One group fell out with the owners of an Audi," Bannerman says, "so they threw their barbecue in it and it went up in flames."

The result of this and much more was a ban, which started last year, on unregulated camping. Visitors must now pay to use official campsites. It's a huge relief for the Twaddles, Bannerman and their community. They say ordinary families who were driven away are coming back, and praise the park authority, but now another set of restrictions is being proposed, and battle lines are drawn over them.

A brisk, cold easterly blows across the loch just north of Balloch, raising choppy, white-topped waves. The ranger patrol boat steers for a cluster of islands: Inchcruin, Inchmoan, Inchtavannach and Inchconnachan. On a tree drooping down towards the water, we see an osprey on her nest. Her mate takes off, his powerful pale wings crushing the air. The ranger, David Cameron, is excited as he hands me binoculars: this is the stuff that makes him want to get on to the loch.

We enter a bay on Inchconnachan favoured by campers, then The Narrows, winding up between the islands. The beaches look idyllic, but Cameron points to the stumps of trees felled for firewood. "They bring the city out here," says Cameron. "It's as if they want to recreate what they have at home, all the boats next to each other, and then they start drinking."

Trouble, damage and litter follow, as do arguments: Cameron has rescued groups marooned on islands after they've fallen out with boat-owners. "You wouldn't want to go behind the beach on some islands because of the crap and toilet paper," Cameron says bluntly. "You do get large groups who behave and bring a chemical toilet and a sense of responsibility. There are people who use the islands properly, but a minority spoil it."

These islands have special protected area status and are home to half a dozen endangered capercaillie. Now, to protect them further, the authority has proposed bylaws restricting camping on these islands from March to October to one or two managed sites.

Days later, cruising here with Peter Jack, it could be a different place. It's sunny and calm, and Jack claims the islands are unchanged since the 1960s. "The biggest change has been those ugly steel things," he says, pointing to capercaillie information signs erected by the park.

Jack chairs the Loch Lomond Association (LLA), representing water-users. His boat is a 32ft motor cruiser. He calls it "caravanning on water". The LLA has fallen out with the authority over water safety issues, and Jack is bitterly opposed to the proposed bylaws.

"It's over-management, it's draconian, it's unnecessary, it's not justified," he says. "Misuse of the islands is by a very small proportion. People are exercising their right to their cultural heritage, which they and their families have been typically doing for 100 years. The park is meant to be upholding the cultural heritage of the loch and the park but they are not recognising cultural heritage when they see it." The capercaillie here, he says, are insufficient to conserve. "The bird has flown long ago," he says.

Jack believes the authority has an anti-powerboat agenda, and the camping ban will hasten the current decline in boat-launchings. Fewer boaters will mean less money spent in shops and pubs, and less work for local boatyards and repairers. "I wonder whether we would be any worse off without a national park," he says. "I wonder if that budget was applied to equip existing authorities and police, we could be better off."

Jack is not alone in opposing the park. Peter Sunderland is director of Gartmore House holiday and conference centre, where the park was officially founded and where its first board meeting was held. "I was in favour of it at first," he says, "but I would have to say, as far as residents are concerned, it has not delivered."

Sunderland believes planners and those who enforce rules are over-fussy, and recounts a row he had with conservation officers over pruning trees when they insisted on a £2000 bat check. He chopped the trees down instead.

"It was this policing mentality they have, rather than saying, 'Let's try to improve the area.' It gets me down. I would much rather the park was scrapped and went back to Stirling Council," he says.

Sunderland also questions the camping bylaws. "They should have staff to patrol it instead of a total ban, and take people's registration number and deal with them if they cause a problem, rather than a ban."

There is a feeling elsewhere that the park is not delivering anything visible. Fiona McEwan, chair of the Strathard Community Council in Aberfoyle, says, "The feedback we most often get is one of disappointment that the impact of the park has been really quite minimal, in broad terms more what it hasn't done rather than what it has actually achieved. Whether it has been value for money is questionable."

Bill McDermott of the Scottish Campaign For National Parks is glad the authority exists, but is unhappy with some planning decisions – such as giving the gold mine being created at Cononish near Tyndrum planning permission last year. He doesn't like the latest five-year plan either. "It looks almost like a local enterprise company trying to boost the economy," he says. "It's being sold on the basis that the national park is an economic opportunity - That is not what the park is there for."

Fiona Logan, the authority's £80,000- a-year chief executive, has a business background and is credited with shaking up its public-service ethos. For two hours at the Oak Tree Inn in Balmaha, words tumble out of her. She won't like the comparison, but it reminds me of John Prescott: enthusiasm for her work sometimes overtakes her ability to express it. You do, however, get what she means and understand her passion for protecting this place.

If government funding is a measure of success, she is succeeding: the park's budget has gone up this year by £1m to £9m. "I think it's because we are out there doing the stuff. We're making brave decisions," she says. I tackle her about camping on the east shore. Would more resources, intensive patrolling and policing, not be a fairer solution?

She says there are too many legal grey areas for extra policing to work, and, talking about what residents and wardens have put up with, she becomes heated. "For 30 years the public sector has dealt with the excesses of Loch Lomond and done absolutely f*** all about it," she says, hastily adding: "Pardon the French. Not long after I was in this job I read a document from 30 years ago which could have been written three years ago – it was word-for-word the same kind of excesses.

"You create a national park which has the West Highland Way running through it, which attracts tens of thousands of visitors, seeing that behaviour, and residents putting up with that - There was massive degradation, chainsaws were being used. For me it goes to the core of what this park was created to do. We were created in a managed landscape to put managed solutions to deal with the visitor pressure."

The bylaws proposed for the islands are one of three options, including leaving things as they are, but Logan is clear that the capercaillie must be protected. The park has a duty under European law to do so and could be fined if the birds disappear. She is aware, however, that bylaws and bans are not the only way. The lochshore bylaws are up for renewal in three years, and she says if the problems are resolved the rules could be softened.

Logan is not committed either to bylaws for other areas of the park away from Loch Lomond suffering wild-camping problems, such as the "Five Lochs" in the park's north-east around Callander, where park funds are to be used on toilets and other infrastructure.

There's little softening on the subject of Peter Jack's LLA from Logan, however. She says relations with Jack have collapsed because of a "fundamental personality breakdown". "Peter Jack just doesn't like me and Grant [Moir, the park's director of conservation and visitor experience]. No amount of talking, no amount of reasoning - The misinformation is unbelievable. It's not even worth commenting on." Jack's suggestion of a bias against powerboats is dismissed by Logan, as is his contention that the islands are unchanged since the 1960s.

Logan defends her planners against Sunderland's accusation of fussiness, saying there are hundreds of satisfied users of the planning department and that there has been a change of culture in the department in recent years, but there are no real answers when I ask what was wrong with the culture before.

She says residents around the eastern shore are satisfied with the clean-up. Without anything comparable, it's perhaps understandable a sense of disappointment lingers elsewhere. But Logan insists there are things going on which don't attract headlines: a grant scheme has given more than £600,000 to landowners and conservation groups for access and conservation, and the park secured £720,000 from the Scottish Government to conserve black grouse at Callander.

One thing which worries many people is the lack of a budget for path maintenance: on hills such as Ben More and Ben Oss eroded paths are becoming scars, and the West Highland Way on Conic Hill is badly worn. Work by the park on hill paths relies on raising funds on top of its budget.

Logan tells me the park is now copying the Cairngorm Park's Outdoor Access Trust, set up to win funds from sources such as the Heritage Lottery Fund to build paths.Surely, I say, with my mountaineer's hat on, upland paths are what a national park should spend core cash on, rather than going cap-in-hand to other organisations for the money?

"A big chunk of our budget is staff because we are a planning authority, and run a ranger service [with up to 66 staff]," she says. "There's a million or so left after that, and it is spread pretty thin."

The same principle applies to public bodies such as the local authorities. Logan says the park's job is not to take over their functions – the councils are still, for instance, in charge of toilets and litter – but to help them do their job better.

She's pleased though that, unlike English and Welsh parks, Scottish ones have a fourth aim of economic development.

As a public-sector body, she says, "you are not going to get anywhere saying, 'Please, we are underfunded, woe is us'". "What you do say," she argues, "is that we will create thriving local economies that will attract private investment into tourist development. We can be as pro-access and pro-conservation as we want, but if there's not the economy to help provide for that, the public sector is not going to help."

Logan cites the example of the Loch Lomond piers: the park spent £300,000 upgrading them, which the commercial boating businesses couldn't afford. They welcomed it, says Logan, despite charges going up, because it secured their future. The extra income will now pay for pier maintenance.

"We are not preserving these parks in aspic," she says. "That's not what ministers wanted when they introduced national parks: they put in a fourth aim. The biggest conservation threat is the visitor pressure, and for me the development agenda is all about giving those people things to see, things to do, places to stay, to eat out and do the walks."

From Balmaha, I cadge a lift back to Balloch with Ali Cush, the park's education officer. She drives carefully but talks with 90mph enthusiasm about her work of getting rangers into classrooms, helping schools with outdoor education, and teaching pupils from schools in the urban sprawl about the park.

"If they haven't any experience of the outdoors, they won't respect it," she says. "When they get older, tents are cheap and they're only a few miles away: they'll come here and have no idea how to behave. We can educate people, and that in itself will mean fewer problems."

On the beach that Sunday, her words come back to me: they have no idea how to behave. As long as the park has to put its efforts into fighting such ignorance, it will struggle to please all its critics. n