Britons are struggling to remember the passwords for an average of 22 online accounts each.
And more than one in six people have over 40 such accounts to keep track of, the Payments Council said today.
Three-quarters of people use the same password for more than one account and more than a third admit to having shared their personal details with family and friends. Almost a third (29%) say they never bother changing their password.
The findings were released to highlight the council's education campaign, PayYourWay.org.uk, which warns that people are increasing the threat to their security by using easy-to-guess passwords.
Some 25% of people surveyed said they keep the memory of their dead pets alive by still using their names in passwords.
The council said that people should steer clear of using the same password, or even a variation of it, more than once, to restrict the damage if the password on one account is compromised.
They could also use a piece of software called a password manager to keep track of their passwords.
This creates random, hard-to-guess passwords for each site someone visits, meaning they only need to remember one single, master password to access them all.
People are also advised to be creative and avoid birthdays, names and common words. One way of doing this is to string together words from a phrase or song lyric.
"The Grand Old Duke of York, he had ten thousand men," could give a password of "TGODoYhh10000m!" for example, the Payments Council said.
Adrian Kamellard, chief executive of the Payments Council said: "These days we have more online accounts than ever before, so it can seem like a lot to remember.
"But you don't have to be a memory expert - these PayYourWay.org.uk tips should keep your vital financial accounts safe by helping you set unique, secure, easy-to-remember passwords."
The Payments Council also teamed up with memory expert Dominic O'Brien, who suggested that people could create a more individual password by creating their own coded story.
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Mr O'Brien said: "Take the password 8:30121hP99. Imagine it's 8.30 in the morning and you're having a one-2-one meeting with little Harry Potter who's holding 99 red balloons."
More than 2,000 Britons took part in the research last month.
