Faulty genes could be the cause of up to 60% of a major form of back pain, according to new research.

A study of 400 twins has found that identical twins with back problems often have similar symptoms and worn-out discs in exactly the same position of the spine.

The research, funded by the Medical Research Council and published in the journal Arthritis and Rheumatism, measured disc degeneration in the neck and lower back with magnetic resonance imaging scans.

Around two thirds of the population are affected by back and neck pain which is the commonest cause of time off work.

It costs industry an estimated �6bn a year in lost production and the NHS �480m in treatment.

Posture

Dr Tim Spector, director of the Twin Research Unit at St Thomas' Hospital in London, worked with Australian researchers on the project.

He said: "Although occupation, posture and injuries obviously play a role in some people, this study shows a worn-out disc, one of the commonest causes of chronic neck and back pain, is largely inherited and the hunt is now on for which genes are involved."

But Emma Tait of the National Back Pain Association said worn-out discs only accounted for 10% of back pain.

The other 90% was caused by a variety of factors, including sports injuries and bad posture.

She added that 50% of the population have a degenerative disc problem, but many do not go on to have back pain.

However, she called the St Thomas' research "important" and "a piece of the jigsaw" which could help doctors treat back pain.

The Association advises people to take regular exercise and adopt correct posture in order to avoid back pain in later life.

Dr Spector is hoping to further his research and is seeking volunteer twin guinea pigs.

Anyone interested should ring 0990 770099. The researchers say they will offer volunteers free screening for a wide number of diseases, including arthritis, asthma and heart disease.