A travel magazine has put Britain's Three Peaks Challenge on its latest list of worldwide destinations in need of greater care.
The challenge features the highest peaks in England, Wales and Scotland - Scafell Pike, Snowdon and Ben Nevis.
Wanderlust has claimed the actions of some entrants harm the environment by leaving litter and causing erosion.
Three Peaks Challenge Limited said it offered advice on how walkers tackle the summits safely and responsibly.
Landscape charity the John Muir Trust, which owns Ben Nevis Estate, said the magazine had raised important issues.
Wanderlust's latest Endangered Destinations List also features sites in China, Kenya, the US and Madagascar.
In its entry for the Three Peaks Challenge, Wanderlust has suggested the numbers of people taking part should be limited.
The magazine said organisers were educating people tackling the challenge to treat the mountains with respect.
Editor-in-chief Lyn Hughes said readers might be surprised to see the peaks on its list.
She added: "Tourism can be a double-edged sword for destinations.
"At the same time as supporting local communities, if things aren't managed properly the negatives can soon outweigh the positives creating major environmental and cultural issues."
Nick Johnston, of Three Peaks Challenge Limited, said he did not believe numbers should be restricted.
He said: "We estimate there's around 30,000 people doing the Three Peaks Challenge this year.
"That compares to a quarter of a million people that are going to climb Snowdon just recreationally."
Mr Johnston added: "One thing we're doing this year is challenge registration.
"It provides a way for people to record their challenge and get recognition but it also gives us a way of giving them advice beforehand, to help them be more responsible and safer."
On its website, the John Muir Trust said Ben Nevis has rare and sensitive wildlife and warned that high visitor numbers contributed to erosion.
It added: "The trust would like everyone who comes to Ben Nevis to enjoy their visit and to help keep Ben Nevis special by adopting a 'leave no trace' approach.
"That means that everything taken up the hill should be taken back down."