Financial provider NS&I's quarterly savings survey found that 27% of those who said they had some emergency cash put by had broken into it for no pressing reason.
One in 14 (7%) of those who hold some rainy day cash thought an appropriate reason to drain their emergency fund would be "to reward myself", and the same proportion said a valid reason was to make an "impulse purchase".
One in five (18%) of those surveyed with an emergency fund said a holiday would be an appropriate reason to dip into their account.
Essential home maintenance, paying bills and becoming unemployed were the most common types of emergency people thought were good reasons for dipping into a fund.
Experts generally believe that people should be saving at least three months' of their salary to put together an emergency fund, but only 45% of more than 2,400 Britons surveyed have at least this amount put aside.
The research conducted in September also found that Britons are now managing to save £96 a month typically, up from £88 the previous quarter.
"And, when we are doing it, how many of us are prepared to dip into a rainy day fund when it is not really an emergency.
"By taking control of your finances, and if possible putting aside some money for a 'rainy day', you can protect yourself should anything unfortunate happen, and have peace of mind that you have your emergency fund to dig in to, in order to help cover the costs of any unforeseen circumstances."
The findings come as savers continue to struggle to find any real returns on their cash, with the Bank of England base rate having been kept at a historic low of 0.5% for more than four-and-a-half years.
David Cutter, chairman of the Building Societies Association (BSA), called on Chancellor George Osborne to do more to ease savers' plight in next month's Autumn Statement.
Speaking at the BSA annual lunch, he said the Chancellor should introduce a range of measures to help savers, including raising the subscription limit on cash Isas and allowing transfers from stocks and shares Isas into cash Isas.
He also suggested that the Government should introduce a "first Isa" scheme, whereby a proportion of the savings of first-time Isa savers could be matched by the Government to help encourage more people to save.
Mr Cutter, who is group chief executive of the Skipton Building Society, said: "Savers remain the bedrock on which our lending industry is based, and it is therefore vital to encourage and foster a long-term savings culture."
© 2013 Press Association