Almost three-quarters of groups that run outdoor fundraising events on Ben Nevis do not inform the authorities in advance, according to Highland Council.
The Institute of Fundraising's code covering outdoor fundraising events says it is mandatory for members to consult landowners before events take place.
Geoff Robson, head of environment and development at the council, said 55 groups had registered with the council last year. He estimated that this accounted for about a quarter of all groups. He said 36,000 fundraisers climbed the mountain every year.
Robson said the council had an online system through which charities could register their events. Those that registered were charged a fee, which was used to cover the cost of clearing up and maintainance.
"It costs us about £25,000 a year to clear up after charity fundraising groups on the mountain," he said. "We receive only £10,000 a year from the charities that do register and pay."
A spokesman for Wales's Snowdonia National Park said the issue was a growing problem. But he said that land managers in England and Wales could not charge groups for access, unlike their counterparts in Scotland. He said he did not have figures on the costs of clearing up after charity fundraising events, but he thought they would be significant.
A spokeswoman for the Yorkshire Dales National Park Authority said large and medium-sized charities often informed it that they would be holding events, but there was less communication from smaller charities.