Research from 'life assistance' company CPP, which provides a variety of advice, insurance and practical help, says we're increasingly relying on mobiles to replace our own memories.

23 million adult Britons – 47% of the population - can't remember their partner's mobile number by heart, 30 million (61%) have the same problem with their best friend's number and 22 million (45%) don't know their parents' mobile number.

However, 92% of adults are able to recall their home fixed-line number and 60% know their parents' landline.

It indicates a serious problem if mobile phones are lost, stolen or damaged. In fact, 67% of respondents said they were anxious about losing the numbers stored on their phones but only 43% had a written backup and even fewer – just 18% – have an electronic copy on their computer.

Michael Lynch from CPP said "Our research shows that people are so heavily reliant on their mobile phones, that they'd be lost without them. And even if not caught in an emergency situation, our research shows that four in 10 victims have admitted that they've lost contact with friends when they've lost or had their phones stolen."

CPP offers five tips for remembering telephone numbers:

Step 1: Visualise the number - picture the numbers in your head. Think about what they would look like, what colour they would be, what they would look like on a business card or in your handwriting.

Step 2: Recite the number out loud. Recite the number three times right away, and again in one minute. Recite them every few minutes out loud. Even create rhythm in the sequence of numbers to the tune of a well-known song.

Step 3: Practise dialling the number. Move the fingers in the way in which it would be used to dial the number while reciting the number.

Step 4: Group the numbers together. The human mind naturally remembers numbers better in groups of three and four.

Step 5: Look for personal associations with the numbers. Associate numbers to birthdays, ages, pin numbers or other things that are personal to you. Your mind will recall the numbers when the association is thought up.