Research by HSBC found about 15 million people in the country have no more than what they earn in five days to fall back on.
This translates as less than £249 as a safety net, which would have to be used in the case of an emergency.
Richard Brown, head of savings at the bank, says: "These findings demonstrate a worrying lack of preparation amongst UK residents. With the current climate of uncertainty, it is of utmost importance that people are setting aside a realistic sum of money."
The latest Credit Action report showed about 9,000 people approach the Citizens' Advice Bureau each day with money problems.
Posted by Jim Tidy
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