The Institute of Fundraising's code of practice on outdoor challenge events has been updated to place more emphasis on the importance of reducing their environmental impact.
The new version of the code, which will be launched this week, applies to all outdoor fundraising events, including the Three Peaks Challenge.
"Organisers of events who knowingly encourage excessive numbers in areas of environmental sensitivity or who do not manage their event to minimise impacts are irresponsible," it says.
It specifies more clearly than previous versions that it is compulsory for all charities that are members of the institute to talk to land managers when organising events. It says it is mandatory for members to leave no trace of the event's occurrence, which had previously been a recommendation for best practice.
The section of the code that covers the Three Peaks Challenge has been updated to stress that national park authorities, local authorities and landowners are operating stronger management regimes for fundraisers.
It says: "If action is not taken to comply with this guidance, the sustainability of the event as a valuable fundraising activity will be severely threatened. Please extend your charity beyond the worthy cause you are raising money for by respecting these areas and their people."
The code says it is mandatory for members to register all groups of 12 or more with the Glen Nevis Visitor Centre. According to the Highlands Council, almost three-quarters of fundraising groups that run events on Ben Nevis fail to do this.