Charity climbers who attempt to scale the tallest mountains in Scotland, England and Wales in under 24 hours to raise money, will today be accused of environmental vandalism and of breaking their own fundraising code.

Each summer tens of thousands of hikers descend on Snowdon, Scafell Pike and Ben Nevis, to try to complete the 10,000ft climb of the Three Peaks Challenge and raise million of pounds.

Officials at the Lake District National Park will today launch a campaign with the Fundraising Standards Board, which monitors charity fundraising, to call for limits on the number of participants in the challenge that has become a favourite among big firms and charities.

They complain that hillsides have been scarred by parties of up to 1,000 hikers at a time, that verges and streams have been polluted with human excrement and urine, and that residents' sleep has been disturbed by vehicles at night.

"Unlike the London marathon, this is not a one-off, structured event, so each weekend during the season many hundreds ... attempt the challenge [for] many different charities," said John Scourse, chief executive of the Fundraising Standards Board. "The impact on the environment and people can be detrimental."

The problems have been felt particularly in the Lake District because a typical itinerary involves climbers starting on Ben Nevis between 5pm and 10pm, then driving to Cumbria to ascend Scafell Pike between 4am and 5am, followed by Snowdownia. Hundreds of vehicles arrive at night in the Cumbrian hamlets of Wasdale and Seathwaite in Borrowdale, as people attempt their 24-hour target.

"People arrive, slamming doors, parking on verges and blocking roads," said Mick Casey, for the Lake District National Park Authority. "They also go up the pike whatever the weather, and if you have 400 people going up a path in the lashing rain it erodes very fast." Deep gullies have been cut in soil next to footpaths by large groups of walkers spreading out. "We are delighted people are using our national park to raise hundreds of thousands for charity, but they have to show some responsibility," Casey said.

The park wants to restrict nightly parties up Scafell to 200 people.

According to some residents in Wasdale, the problem has worsened in recent years and there is worry about this summer's climbs, from June to August. Howard Christie, landlord of the Wasdale Head inn, said: "There can be 600 people going up, 600 going down again ... At three in the morning you hear nothing but the beep beep of reversing minibuses and voices saying 'Is this Scafell? Is this Wasdale?'."

Richie Evered, director of Merseyventure, which organises the Three Peaks Challenge for some charities, defended the charity hikers and said he already restricted his groups to 200 people. "There are a lot of independent teams [who] are completely unaware of the lack of facilities in the area. It's a small minority of locals who complain. We are trying as hard as we can."

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