Being within sight of the summit can encourage climbers to take risks

Dr Andrew Sutherland, a medical advisor on Everest expeditions, says unofficial figures show 15 people died in 2006.

The death rate has remained at one death for every 10 successful attempts to climb Everest for many years, the British Medical Journal report states.

Dr Sutherland says poor understanding of the effects of altitude is to blame.

The longer you stay up there, in the death zone, the greater the chance you have of dying

Dr Andew Sutherland

It is 53 years since Edmund Hillary and Sherpa Tenzing Norgay became the first people to conquer Everest.

Dr Sutherland, an Oxford-based surgeon, says there is now be a better understanding of the need for acclimatisation, the kind of climbing equipment which is required and established routes for people to climb.

That meant there should be fewer deaths he said. But that is not the case.

While most deaths are caused by injuries and exhaustion, there is also a large proportion of climbers who die from altitude related illness.

High altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are both forms of altitude sickness which cause a potentially fatal build up of fluid in the brain or lungs.

'Altitude ability'

Dr Sutherland, who climbed the north side of Everest this year on the Everestmax expedition, said he was shocked by the amount of altitude related illness and the relative lack of knowledge of the dangers among people attempting Everest.

"From being there, I saw there were a lot of people with considerable mountaineering experience, but who were fairly naive in some ways about the extreme altitudes they were going to face."

Dr Sutherland said the common belief that the deaths were largely among inexperienced climbers who pay large sums of money to climb the mountain.

But he said those people tended to have very experienced guides which meant they were at less risk than independent climbers.

But Dr Sutherland added: "In my view, climbers are not climbing beyond their ability but instead beyond their altitude ability.

"Unfortunately it is difficult to get experience of what it is like climbing above Camp 3 (8,300 metres) without climbing Everest.

"Climbers invariably do not know what their ability above 8,300 metres is going to be like.

"The longer you stay up there, in the death zone, the greater the chance you have of dying."

'Right to climb'

He said climbers needed to check that they were not climbing too slowly - a sign something is wrong - and turn back if need be.

The slowest safe rate is around 100 metres every one to one-and-a-half hours. If progress is any slower than that, people should abort their attempt.

But he said people's egos meant they often did not listen to their bodies.

"With the summit in sight this advice is too often ignored."

Dr Charles Clarke, a neurologist and head of the British Mountaineering Council, said mountaineering had inherent dangers which climbers needed to take precautions against.

"Anybody who wants to can climb Everest. We respect people's right to do that.

"But no one can say 'I wasn't told about the medical risks'. People have got to be fully aware of that."