A payday lender has apologised to customers who received emails threatening to contact their employers if they did not settle their debts.
The National Debtline says it heard of numerous cases where MiniCredit acted in an overly aggressive manner.
MiniCredit says it has taken steps to ensure it does not happen again
The Office of Fair Trading (OFT) says companies should not act in a way that is likely to cause debtors public embarrassment.
27-year-old Emma Burgess from Manchester took out several payday loans last year when she had to move out of a shared flat and needed money to cover the cost of new accommodation.
When she found herself unable to pay back her first payday loan she borrowed more cash from another lender to pay it off.
But her debt soon spiralled until she owed money to seven payday loan providers.
"I sought advice from a debt charity and they told me that I should be able to negotiate repayment plans," she told5 live Investigates.
"I'd gone to the effort of getting an expenditure form and working all of that out.
"I'd sent that off to other companies who had seen what I could afford to pay and they understood what I offered them was reasonable and they accepted the plans."
Miss Burgess says MiniCredit was the only creditor to refuse to help her manage her debts. Instead, she received a reply saying they might contact her employer and start legal action against her.
"It was quite worrying being sat at work and wondering whether, when the phone rings, it's going to be them speaking to your boss about your financial problems," she says.
"It's quite embarrassing. I didn't want people at work knowing what was going on. It would have been quite awkward for me."
OFT guidelines on debt collection state that it is improper for companies to act in a way "likely to be publicly embarrassing to the debtor".
Companies must comply with OFT guidelines if they are to hold on to their licence and significant breaches can lead to a licence being revoked.
MiniCredit also threatened to send Miss Burgess's case onto a doorstep collector if she did not pay her debt in full within 10 days.
"It was scary, the thought of being at home on my own and having people come round to my house."
While MiniCredit refused Miss Burgess's requests for help, her debts with them continued to mount.
When her account was eventually passed on to debt collectors, her original £100 loan had spiralled to £750.
She is now paying back £50 a month.
5 live Investigates has spoken to several other MiniCredit customers who say the lender refused their requests for help in managing their debts.
The programme spoke to another customer who also received an email from MiniCredit threatening to contact their employer if their debt was not settled.
When the BBC contacted MiniCredit about these cases its director Andres Valdmann initially denied the company had ever threatened to contact any of its customers' employers.
But in a subsequent statement, the MiniCredit said: "If a customer is struggling to pay back a loan it is not company policy to contact their employer.
"We apologise if customers have received misleading correspondence from MiniCredit about this matter.
"We have taken steps to ensure that this situation will not occur again."
MiniCredit also said it was company policy to create settlement plans for any customer having difficulties repaying their loan.
The number of people taking out payday loans in the UK has more than quadrupled since 2006.
Latest figures show there are more than 1.2 million payday loan borrowers in the UK.
Last year MiniCredit issued more than 100,000 loans, however the Financial Ombudsman Service received more complaints about MiniCredit than any other payday lender in 2011.
The trade body, the Consumer Credit Trade Association (CCTA), of which MiniCredit is a member, has told the BBC they have also received complaints about the company.
The CCTA says it has warned MiniCredit that unless the company stuck to the OFT guidelines, it would risk getting in trouble with the regulator.
The debt advice charity National Debtline has also expressed concerns about the company.
"Our advisers have reported numerous cases where MiniCredit has acted in an overly aggressive manner, refused sustainable repayment offers and refused to freeze interest and charges," says the charity's chief executive, Joanna Elson.
"Collections practices like these contravene the Office of Fair Trading's Responsible Lending Guidance."
MiniCredit told 5 live Investigates: "Bearing in mind the number of loans MiniCredit provided last year, the total number of complainants [to the Financial Ombudsman Service] was incredibly small - 54, which equates to 0.05% of loans issued.
"The vast majority of our customers are happy with the service they receive from us.
"Following a constructive conversation with the Financial Ombudsman Service, we have improved our complaints handling procedures.
"As a one-off gesture of goodwill, MiniCredit is settling all complaints lodged with the FOS last year.
"We would like to apologise to affected customers if the service they received from MiniCredit did not meet their expectations or the high standards we set ourselves as a company."
The Office of Fair Trading recently announced it is toinvestigate 50 payday loan firmsfollowing concerns that they have been pushing loans to people who cannot afford to repay them.