The Office for Fair Trading (OFT) has closed 19 unlicensed lead generation websites, which were selling on people's data to other businesses.
The sites, which claimed to offer loans, targeted people with disabilities, those connected to the military and people with generally limited access to credit.
With the assistance of web hosts, or via the businesses themselves, all 19 were shut down.
The OFT said it will continue to monitor the situation to see if the sites reappear with different hosts.
"Websites like the ones we have shut down target vulnerable people and those who may not have easy access to credit," said David Fisher, OFT director of consumer credit.
"We advise consumers to think carefully before entering personal data into any lead generation website, in case this information is passed on without their knowledge."
Lead generation companies which sell on user data need licenses, which they can acquire from the OFT.
The body warned people they may find they have to cope with unwanted contact from a number of companies if they hand their data over to lead generation businesses.
See below for the list of sites found to have breached the Consumer Credit Act:
www.loansfordisabledpeople.co.uk
www.samedayloansforpeopleonbenefits.co.uk
www.militaryloans.org.uk
www.cashloansforpeopleonbenefits.org.uk
www.urgentloansbadcredit.co.uk
www.cashtoday.me.uk
www.cashpayday.me.uk
www.debitcardinstantloans.co.uk
www.cashloansunsecured.co.uk
www.loansforpeoplewithbadcredit.me.uk
www.samedayquickloans.co.uk
www.loansfordisabled.co.uk
www.unsecuredloansforpeopleonbenefits.co.uk
www.loansforpeopleondisability.co.uk
www.refusedaloan.org.uk
www.paydayinstallmentloans.co.uk
www.nofaxcashloans.org.uk
www.nofaxpaydayloan.me.uk
www.loansfortheunemployed.org.uk
