Payday lenders have been accused of "irresponsible behaviour" which is trapping people with loans they cannot afford.
A study by Citizens Advice found that some companies were still failing to carry out basic checks to make sure borrowers can afford to pay back loans.
A survey of over 400 people who had attempted to use payday loans revealed that one in four had not, or could not remember, being asked questions about their financial situation or ability to repay a loan.
A separate study of Citizens Advice staff and volunteers showed that 27% said inadequate credit checks were the main cause of problems to the people they help.
The research in England and Wales found that fewer problems had been reported since a cap on payday loan interest rates was introduced in January 2015.
Citizens Advice helped one 33-year-old man who was granted a payday loan following checks despite suffering from depression and alcoholism, having no permanent address, being previously declared bankrupt and having only benefit income.
The report finds that half of these borrowers are still getting into difficulty paying back their loans. This increases when looking just at people who did not go through credit checks with 78% getting into difficulty compared to 40% who did have checks.
Those surveyed said it was easy to get a payday loan, using online and phone applications, with few requiring credit checks.
The report also highlighted new methods being used to collect payments from people's accounts. Citizens Advice found a number cases where a payday lender asked people to share their internet banking details including login and password so a lender could directly access their account and adjust funds without advance permission from the borrower.
Gillian Guy, chief executive of Citizens Advice, said: "Irresponsible behaviour by some payday lenders is trapping people with loans they can't afford.
"New measures and guidelines from the Financial Conduct Authority have helped to clean up the market and the number of people turning to us for help has dropped significantly. But it's clear some payday loan firms are flouting the FCA's guidance and selling people loans costing hundreds of pounds that they struggle to pay back.
"The time has come for the FCA to turn its guidance into rules, forcing every single payday lender to carry out rigorous financial checks on potential borrowers to prevent people falling into deepening debt."
Russell Hamblin-Boone, chief executive of the Consumer Finance Association, which represents short term loan firms, commented: "It is unfortunate this report fails to acknowledge the significant changes in the regulated short-term lending sector and we don't recognise the picture of the industry it paints. "