Around two-thirds of over-55s are concerned the would not be able to raise the necessary cash if faced with an unexpected payout of £500 or more, according to the Aviva Real Retirement Report.
The report, released on Wednesday, says 92% of pensioners have faced unexpected expenses over the past five years, but 55% have made no provision for unplanned outlays, presenting a worrying prospect.
Aviva's research says only 6% of over-55s have made provision for long term care, 9% for private medical care and 23% for the upkeep of their homes.
Almost half of pensioners expect to be forced to dip in to emergency savings funds and a quarter predict they will use income-generated savings to meet unexpected bills. Credit cards, loans, the sale of assets and cut backs in other areas were also revealed as methods of making ends meet.
The average pensioner in the last quarter had an income of £1,313, with 59% of over-55 households living on between £751 and £2,500 per month. However, there are also extremes; 21% of over-55s receive more than £2,501, whilst another 21% live on less than £750.
Older pensioners aged between over 65 are more heavily reliant on the state pension, whilst almost a quarter of people aged between 55 and 64 count earned income as their largest single source of income. High levels of redundancy and unemployment are demonstrated by the heavy reliance of pre-retirees aged 55-64 on state benefits.
Over 55s, the report says, will live on average to 88, retiring at 63 and having worked for 44 years. This, Aviva analysts say, is a "difficult imbalance" considering how little the majority of people save each year.
"When you consider that for a savings pot of £16,296, you would get an annual gross income of just £117 from the standard branch based notice account, you can understand why many over 55s are very worried about their finances," says Clive Bolton, at retirement director for Aviva.
"These figures reveal one in five over 55 households is struggling to get by on almost a third of the national average income. Retirement income is also relatively fixed which is why any rise in the cost of living is particularly concerning for this age group."
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