Complaints about payday loans have rocketed over the last six months, with the Financial Ombudsman saying borrowers have become more aware of their rights.
Official figures show that it received 4,186 complaints in the first half of the year - three times as many as during the previous six months.
"Lots of factors can influence the complaints we see, from more people knowing more about their rights when things go wrong, to external factors like volatility in the stock market or extreme weather conditions," says chief ombudsman Caroline Wayman.
The increase in complaints about payday loans follows new measures and guidelines from the Financial Conduct Authority. Since January last year, loans have been capped at 0.8% a day, and default charges limited to £15.
In addition, the total cost - fees and interest - is capped at 100% of the original sum, so that nobody should ever have to pay back more than twice what they borrowed.
However, a recent study by Citizens Advice found that some companies were still flouting the rules by failing to carry out basic checks to make sure borrowers can afford their repayments.
"However, we are concerned that some less scrupulous firms could be breaking the strict rules on lending."
The latest figures show that while the number of complaints about payday lenders has increased, the proportion of cases that are upheld has dropped. Ironically, many cases are launched with the help of claims management companies - frequently the subject of complaints themselves.