The gun is designed to zap its victim with an electric current, using a laser to carry the charge along a beam of ultraviolet light.

The light particles, called photons, would create a path through the air that will be capable of conducting electricity up to a distance of about 100 metres (330 feet).

When the current hits someone, it would interfere with the tiny electrical charges that control the victim's muscles, making movement impossible.

Vital organs protected

But vital organs like the heart and diaphram would not be affected because they are protected by a greater thickness of body tissue.

Corinne Podger of BBC Science: "The stuff of science fiction".

Weapons that freeze muscles are already on sale in the United States, but in order to work they have to be held against the victim's skin. They also have to be recharged after each use.

Apart from having a considerable range, the new 'freeze ray gun' could in theory be fired around corners if mirrors were used. It could also have a constant power source.

Talks in California

The gun is the brainchild of American inventor, Eric Herr, vice-president of HSV technologies. Scientists from the UK's Defence Evaluation Research Agency have already been to California to discuss it with him.

No details of the discussions have been disclosed, but a spokesman for the UK Ministry of Defence said the weapon's potential uses were being considered.

So far, Mr Herr's ray gun remains just an idea. He has taken out a patent on the device, but has yet to raise the $500,000 needed to build a full working prototype.

'Ideal weapon'

Initially, the 'freeze ray' could be the size of a small suitcase, but might eventually be reduced to something more like a flashlight.

Mr Herr believes it could be an ideal weapon for peace-keeping forces, or police facing violent criminals.

But already the project has its critics. They argue that such a laser would be impractical in many situations, and could easily damage the sight of innocent by-standers.