Some people are agreeing to make payments they cannot afford
Banks are being accused of pressuring customers who have financial problems to take out expensive loans to try to ease their debts, the BBC has learned.
Some banks are repeatedly telephoning customers to try to get them to take out costly loans, against the advice of debt charities.
Citizens Advice said it had received many complaints about the increasingly aggressive tactics being used.
Banks say interest rate charges are up to them.
The BBC's Breakfast programme has discovered some customers who have an agreed debt repayment plan with a debt advice charity are being put under pressure to take out loans, sometimes at a higher interest rate than they are already paying.
One HSBC customer, Simon Chandler, said that even though he had declined the bank's offer of a "managed loan", they had continually telephoned him to try and make him change his mind.
The interest rate on the managed loan is 13% - double what he is paying at the moment.
Simon Chandler says he is being pressured by his bank
He said: "I have had multiple letters from HSBC saying they want to help people in financial difficulty - when clearly they don't.
"HSBC have agreed that the amount I can repay each month is acceptable. But the only way they will accept that repayment is if I enter in what they call a managed loan."
In a statement HSBC said: "As a responsible lender HSBC only offers a managed loan to customers when all other lending options have been exhausted. Mr Chandler's loan is flexible and affordable.
"Now back in full time employment he can make additional monthly payments when possible and his interest rate can be revised after a period of good repayment - typically just one year."
WHAT IS A MANAGED LOAN?
Only offered to customers in financial difficulty
Interest rate will be higher than for "good risk" customers
But the rate is lower than for "bad risk" customers
Offered over a longer term compared to normal loans
Interest rate can come down after a year
Citizens Advice (CAB) said it was aware of many cases in which people in debt have offered to make payments where the bank has asked for more than they can afford.
In some cases, customers had asked their bank to deal with a debt advice charity, yet they were still being sent aggressive letters and receiving pushy phone calls.
Peter Tutton from CAB said: "We see a lot of cases of people coming in who have tried to talk to their banks about arranged payments and they haven't been listened to, and they have been asked for more than they can afford.
"Typically people find that, even after they have been dealing with us, they have found that they have been continued to be written to. They get aggressive letters and phone calls from their lenders."
The banks' organisation, the British Bankers' Association (BBA), said banks were happy to work with debt advice charities.
However, it said they have to make their own judgement about the interest rate they charge and how much someone can afford.
Eric Leenders from the BBA said: "The work that banks do with intermediaries like money advice trusts are essentially negotiations - they are not necessarily conclusive."