Doctors should be taught to hypnotise patients not to feel pain instead of using general anaesthetics during some operations, the Royal Society of Medicine will be told today.

In what he has described as a "clarion call to the British medical profession", Professor David Spiegel, of the Department of Psychiatry and Behavioural Sciences at Stanford University in the US, will also call on the National Institute for Health and Clinical Excellence (Nice) to add hypnotherapy to its list of approved therapeutic techniques for the treatment of conditions ranging from allergies and high blood pressure to the pain associated with bone marrow transplantation, cancer treatment and anaesthesia for liver biopsy. Nice has already approved the technique for the treatment of irritable bowel syndrome.

"It is time for hypnosis to work its way into the mainstream of British medicine," Spiegel will say at the joint conference of the Royal Society of Medicine, the British Society of Clinical and Academic Hypnosis and the British Society of Medical and Dental Hypnosis.

"There is solid science behind what sounds like mysticism and we need to get that message across to the bodies that influence this area. Hypnosis has no negative side-effects. It makes operations quicker, as the patient is able to talk to the surgeon as the operation proceeds, and it is cheaper than conventional pain relief. Since it does not interfere with the workings of the body, the patient recovers faster, too.

"It is also extremely powerful as a means of pain relief. Hypnosis has been accepted and rejected because people are nervous of it. They think it's either too powerful or not powerful enough, but, although the public are sceptical, the hardest part of the procedure is getting other doctors to accept it."

Professor Marie-Elisabeth Faymonville, head of the Pain Clinic at Liege University Hospital in Belgium, who has operated on more than 6,000 patients using hypnosis combined with a light local anaesthetic, said: "The local anaesthetic is used only to deaden the surface of the skin while a scalpel slices through it. It has no effect inside the body.

"The patient is conscious throughout the operation and this helps the doctor and patient work together. The patient may have to move during an operation and it's simple to get them to do so if they remain conscious. We've even done a hysterectomy using the procedure."

The theory behind medical hypnosis is that the body's brain and nervous system can't always distinguish an imagined situation from a real occurrence. This means the brain can act on any image or verbal suggestion as if it were reality. Hypnosis puts patients into a state of deep relaxation that is very susceptible to imagery. The more vivid this imagery, the greater the effect on the body.

Dr Martin Wall, president of the Section Hypnosis and Psychosomatic Medicine at the Royal Society of Medicine, said hypnosis fundamentally alters a subject's state of mind. Hypnosis is not, he said, simply a matter of suggestibility and relaxation.

Nice said it would welcome submissions for hypnotherapy to be considered as an approved therapeutic technique on the NHS if it could be cost-effective, and consistent delivery could be guaranteed.

But Professor Steve Field, who chairs the Royal College of General Practitioners, said he was sceptical as to whether hypnotherapy could meet these standards.

"It is a useful tool used by some GPs and patients for relaxation, but I don't think it is something that we should support being rolled out to all medical students and all doctors," he said.

"We can't call on the NHS to support it without there being a firm medical and economic basis, and I'm not convinced those have been proved to exist."