Millions of people in Britain have too many pin codes to keep track of, it has been claimed.
Research from Abbey found that 16 million Britons resort to writing their pin down in order to remember it, with 2.4 million risking fraud by keeping it with their card.
Similarly, 5.7 million use the same number for multiple credit or debit cards, meaning that once one is breached, criminals may have access to all of their accounts.
And such a crisis may result in thousands of people taking out loans in order to get their finances back on track.
"We really do urge you to try and commit them to memory rather than write them down. Otherwise it's like signing a blank cheque for fraudsters," said Steve Shore, head of banking at Abbey.
Meanwhile, money charity Credit Action has claimed that the UK currently has a personal debt totalling £1.3 trillion.
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