Britons are so reliant on data stored on their mobiles that most cannot remember their best friend’s phone number, according to a survey.

More than 60 per cent of those polled could not recall their friend’s mobile number and nearly half (47 per cent) were unable to remember their partner’s number.

Relying on data stored on our mobiles has caused a "numerical amnesia" which could be dangerous in an emergency if a handset was lost, stolen or damaged, the research by insurance and identity protection firm CPP said.

To discover the extent of the nation’s numerical amnesia, the survey included an online memory test. It revealed four out of five people in the UK were unable to remember a mobile phone number after only five seconds of seeing it.

Psychologist Glenn Wilson, who considered the findings, said: "As technology gets more sophisticated, our own memories are on the decline as we increasingly rely on information stored on phones and online."

He added: "This can be problematic if people are totally dependent on an external memory store that is lost or becomes temporarily unavailable. It can also affect an individual’s mental agility later in life. Like many other skills, memory needs exercising if the capacity is not to be lost."

Land line numbers proved easier to remember – 92 per cent of those polled could recall their home number and 60 per cent even knew their parents’ number. A total of 2,019 UK adults surveyed by ResearchNow last month.