The US-based Professional Association of Diving Instructors (Padi) course, which is undertaken by a million people a year, was singled out for allowing beginners to gain an advanced level after just eight dives, four of them in a pool.

A diving expert and a police diver said that people were risking death by going out with insufficient training and experience. Philip Bryson, head of the Diving Diseases Research Centre in Plymouth, told one hearing: “I do not believe that someone with eight dives should be classified as an advanced diver. It is madness.”

Peter Tapper, a diver with Devon and Cornwall police, said: “The whole process moves along far too quickly.”

Nigel Meadows, the Plymouth Coroner, was told that the common factors in the deaths last June were existing medical conditions, alcohol and a lack of experience.

Mark Jackson, 41, from Southwell, Nottinghamshire, dropped his weights when his diving partner ran short of oxygen. He died from an embolism when air trapped in his lungs formed bubbles in his blood.

In a separate incident, Albert Tythecott, 65, from Barnstaple, North Devon, suffered a cerebral gas embolism due to rapid decompression.

Christopher Sidgwick, 40, of Chelmsford, Essex, drowned after he mistakenly used a reserve tank of air that ran out. A verdict of accidental death was recorded at all three inquests.

Padi defended its course, saying: “Accidents do occur.”

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