Many Britons are welded to their smartphones 24 hours a day and refuse to turn them off in cinemas and theatres, according to a study Thursday showing how the devices are changing social behaviour.

Research for telecommunications watchdog Ofcom showed that more than a third of adults and a majority of teenagers say they are highly addicted to devices such as the iPhone and BlackBerry, often referred to as 'CrackBerry' by users for this reason.