Lazing around this Bank Holiday, we should raise a glass to Atta Sherpa, the Nepalese guide who has just broken all records and reached the summit of Everest for the 18th time.

For while we battle with bedding plants, Atta dallies in the death zone, hoisting a constant stream of fat, unfit, oxygen-starved Westerners into one of the most hostile environments on the planet. However reluctant the lobelia, they cannot really compete with that.

We may mourn the vulgar circus that Everest has become - with wealthy egotists queuing like ants to conquer it - but we should feel justifiably happy for 48-year-old Atta, who is fêted as a result of his exploits on the mountain.

Well fed and well clothed, he and his colleagues are now recognised and recompensed for the unique skills they offer the developed world at play.

But there is a darker, hidden story to be told about mountain guides; one born of this burgeoning age of adventure imperialism.

This one is a direct consequence of the extraordinary growth in charity trekking: the fashionable way for thousands of Europeans to raise money for good causes while having a jolly good time in an exotic place. The Andes? The Great Wall of China? Easy peasy to organise.

Everest is not yet on the mainstream charity challenge circuit - give it only time - but Kilimanjaro firmly is. The peak, the highest in Africa, and at 5,898m (19,340ft) the world's highest free-standing mountain, is not only iconic; it is the tallest that can be climbed without ropes or technical mountaineering skills. Purpose-built for the punters, in other words.

This year some 25,000 Westerners will beat the well-worn tourist path to its summit from the Tanzanian side - like Ben Nevis with bells on. I know of some who plan to go this summer: good people, keen on a low-risk adventure, with plenty of creature comforts on the way, and no desire to carry their own packs. But how many will notice their obliging Tanzanian escorts, Africa's forgotten sherpas, who, despite being ill-equipped, untrained and underpaid, will act as beasts of burden during their week-long trip?

The plight of the Kilimanjaro porters is one of those quiet scandals which no one likes talking about, least of all the companies which organise the lucrative trips. But by Western standards what is happening there represents the kind of exploitation stopped on Everest some years ago.

Up to 20 guides and porters die on Kilimanjaro every year. They will die from altitude sickness, hypothermia and pneumonia brought on by inadequate equipment and the relentless, competitive pressure to keep working.

That figure, shockingly, is more than double the number of tourists who die on the peak every year. Moreover, the guides are young men: by the time they reach their 30s they are finished; their bodies burnt out by the pounding they take. The oldest, currently, is 32.

For despite the advertising pitches, Kilimanjaro is no walk in the park. For anyone. Altitude sickness is an ever-present threat, and there is permanent snow on top, with frequent blizzards and temperatures well below freezing.

Every year eight to ten of the 25,000 who set out to climb it will die, usually as a result of altitude; and the failure rate for the climb is startling, with six out of every ten people unable to reach the summit.

On one British expedition last year, only nine out of 35 tourists summited, and 12 of the group had to be stretchered off the mountain. (The national park, although regulated, is too poor to have helicopter rescue or defibrillators stationed on the hillside.)

With a calculated lack of compassion, Western travel companies routinely employ doctors to care for their guests, but not the guides and porters.

Of the 150 guides registered with the Kilimanjaro National Park, most are self-employed. These young men exist in a ruthless free-market economy, vying with each other for the jobs, and risking their own health with enforced lay-offs and lack of proper re-acclimatisation. Their pay is correspondingly cut-throat. Porters (who carry 20k packs containing water, food, firewood and the tourists' possessions) earn $3 a day; guides up to $10.

Set against the £2,500 the individual tourist must raise in sponsorship, both to cover their jaunt and aid charity, these sums speak for themselves. They are, however, well above the average Tanzanian wage.

Allegedly some companies do not pay their staff any salaries at all, but let them rely on tips; and notably, I could find no companies which actually stated on the internet what rates they paid their native staff (though there was copious information about how little impact their long-haul flight would have on the environment).

Guides and porters also have to fund their own equipment. Meaning that trekkers are regularly escorted to the roof of Africa by shivering Tanzanians wearing wellies and flimsy anoraks - both bought secondhand, for up to $30 a throw - and lacking gloves, hats or sunglasses. One British doctor, who bluntly describes the situation as exploitation, had to treat his porters for snowblindness.

Through this GP, I met one of the guides, a slight, softly spoken African of 24 who came, like them all, from abject, mud-hut poverty. He spoke matter of factly about life on the mountain - of being forced to eat the tourists' leftover food, and sleep five in a bed, in shelters lacking any kind of insulation, while tourists enjoyed luxury A-frame huts. He worried not about his own health, but the responsibility he felt when tourists fell sick.

And, of course, Kilimanjaro raises the universal issues of tourism - casual labour, viable wages, exploitation. But it also demands urgent debate about how, in the playing of these supposedly philanthropic games in the developing world, we behave like the worst kind of colonials from a past era.

Let us not kid ourselves: there is nothing heroic left in any of this. Not in the checkout queue at thetop of Everest; neither, especially, on some naive sponsored walk in Africa.

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