Last updated at 08:03 30 May 2007

Booming sales of laptops have led to a surge in the number of computer users with back and muscle problems, experts have warned.

Girls as young as 12 are being diagnosed with nerve damage caused by slouching over screens, a group of leading chiropractors said.

Millions of others are at risk of

"irretrievable damage" to their spines, necks and shoulders because of poor posture when using laptops, it was claimed.

Back specialists say as many as four in five patients have chronic nerve damage caused by working on portable PCs.

The problem is being driven by falling prices and the increasing availability of wireless technology, which makes portable computers more attractive.

Laptop sales in PC World went up by more than 25 per cent last year.

In addition, laptops used at work are not subject to the same health and safety regulations

as desktop computers.

This makes it more likely they will be used incorrectly.

A common problem is perching a laptop on the legs so users stare down at the screen and put strain on their necks, spines and legs.

London-based chiropractor Michael Durntall was among those calling for more research into the issue.

He said he had seen dozens of Xrays showing signs of degeneration in the joints of regular laptop users.

Mr Durntall added: "Mothers bring in their 12-year-old daughters suffering back pain and when they arrive I can see their slumped posture straight away.

"I also see many people in their twenties and thirties with a dowager's hump - a rounding at the base of the neck - after only a few years of looking down at a small screen while sitting slumped on a chair for long periods."

Rishi Loatey, a chiropractor from Wembley, North-West London, said he often treated back and neck pain caused by using a laptop on the move, such as on a train.

Nicola Hunter, a physiotherapist and occupational health specialist, said that hand and arm pain similar to repetitive strain injury was easily induced by resting wrists against the edge of a laptop.

She added: "There's evidence that it stops the nerves and tendons moving as they normally would, and this can cause nerve injury."

There are more than five million laptops in circulation in the UK.

They account for 70 per cent of all computer sales, according to PC Pro magazine.

The problem of laptop-related pain is yet to be properly examined by the Health and Safety Executive.

The HSE merely advises users to follow guidelines

for general computer use, but take more breaks.

Chiropractors recommend the use of a docking station, which links a laptop to another screen and keyboard, or a stand which raises the screen to a higher level.