Out-of-control payday loan companies are disregarding a code of conduct on responsible lending and leaving families drowning in the misery of unmanageable debt, a leading advice agency has warned.

Citizens Advice Scotland (CAS) revealed it had helped 50 people a day last year who were unable to repay a personal loan.

Its sister charity in England and Wales published a survey showing companies were still lending to people who were aged under 18, had mental health issues or were drunk when they took out the loan.

CAS spokeswoman Lucy Manson said there was equal concern about payday lenders operating north of the Border. She criticised companies for failing to adhere to a voluntary code of conduct introduced last November, with high interest rates, poor background checks and harassment among the common complaints.

The agency has been carrying out a survey to check whether companies are following the code. Ms Manson said: "Stories from customers south of the Border show that in many cases, lenders are falling short of keeping these promises. Unfortunately, our evidence here in Scotland shows that this echoes Scots' experiences."

The claims come at a time when Britain's biggest payday lenders risk being put out of business if they cannot prove to the Office of Fair Trading (OFT) they are behaving responsibly. The OFT is expected to announce whether it will refer the payday market for an investigation by the Competition Commission in June.

Citizens Advice said the OFT must take tough and immediate action after the trading watchdog gave 50 payday lenders a 12-week deadline in March to prove their good behaviour.