The Office of Fair Trading has shut down 19 websites which solicited personal information from vulnerable borrowers in order to sell it on.
The lead-generation firms targeted people with disabilities, those connected to the military, and people with generally limited access to credit. An OFT investigation found they were unlicensed and therefore in breach of the Consumer Credit Act.
If the information is sold on, the victims could find themselves being targeted by other companies offering credit.
The OFT is already investigating cold calls and texting by credit brokers and debt management firms.