Mobile radiation shields as much use as chocolate teapots

Some mobile phone shields that purport to protect users from radiation aren't as effective as they make out to be.

According to a report from the US Federal Trade Commission, some devices can actually cause phones to emit even more energy by acting as a focus for channelling power.

The FTC said it had filed charges against two companies who used unsubstantiated advertising claims like "prevents electromagnetic waves from penetrating the brain" and "blocks up to 99 per cent of the radiation".

The shields are coin-sized shield devices intended to cover phone earpieces.

Medical researchers said the radiation emitted by mobiles is not harmful but are unsure what the long-term effects of phone use are.