More than one in four debt-ridden adults fell further into the red during the last three months, new research has revealed.
The study by price comparison website MoneyExpert.com also found that one in ten of those in debt are "very concerned" over their ability to cope.
It claims that equates to as many as 3.4 million people potentially unable to manage their borrowing.
Sean Gardner, chief executive of MoneyExpert.com, said with Christmas looming, that figure could increase.
He called upon those struggling with their finances to take action as soon as possible and said there are many options open to those having difficulties.
"Whether you need to consolidate your debts with a loan or just juggle your borrowing onto cheaper products, the important thing is to work out a repayment plan and not bury your head in the sand," urged Mr Gardner.
Research conducted earlier this year by moneysupermarket.com found more than five million Britons believe they will always have debt.
It highlighted that personal debt within the country grows by £1 million each minute.