The Money Advice Service said it had found a "surprising prevalence of escape funds". The average amount of the hidden pots, designed to enable exit from a marriage or serious relationship, was around £7,500.
Some 9% of married adults admitted they currently have an escape fund, while an additional 14% said they had one previously.
The research, carried out amongst 2,000 UK adults in a serious relationship, found 13% had a secret stash of cash, which their partner didn't know about.
A further 15% admitted to previously having money secretly squirreled away.
About a quarter said their partner would be 'upset, angry or surprised' if they knew the true state of their finances.

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Most (41%) cited 'financial independence' as the reason for keeping their money secret.
Some 38% were worried that their partner would want to spend the money if they knew about it. One in five kept their cash on the quiet as they wanted to be sure their partner didn't just like them for their money.
Corinne Sweet, psychologist and psychotherapist, and author of Stop Fighting About Money, said:"Talking about money is often still a taboo for couples as it evokes feelings of vulnerability and dependency. Many couples hide their true money status as they need to control the power in the relationship. Having money secrets, or a secret escape stash, is likely a way of showing that you have doubts about the relationship.
"The biggest challenge in a relationship is establishing openness and transparency, and that takes trust, effort and time. It is fairly essential to get your 'money baggage' out in the open at the start of the relationship, and try and clear up any nasty (or nice) surprises as you go along as secrecy can eat away at the infrastructure of a relationship."
Nick Hill, a money expert at the Money Advice Service, said: "We like to think that the person we choose to share our life with will always be honest with us but our research shows that, even for married couples, this may not be the case.
"It may be upsetting to find out your partner is hiding money from you, but finding out they are in significant debt could be much worse with consequences for your own finances."