According to a note on the Fos website, these fraudsters are falsely using the watchdog name “to try to persuade people to reveal details about their personal and financial circumstances”, and making things look authentic by getting the Fos number to appear on caller ID.
The ombudsman warned that their officials don’t “write to or phone people out of the blue to ask for personal information”.
It said: “We would only contact you if you've been in touch with us to register a complaint - and then we would only speak to you about that complaint.
“We're a free service so we will never ask you for money and we don't pay compensation to you directly.”
This is the second time the regulatory body warns customers about scammers, since a similar note was issued in 2016.
The Fos is urging consumers to get in touch if they’ve been targeted by these scammers, since the information could help to “crack down on the fraudsters”.
The ombudsman free phone number is 0800 023 4 567.
The Fos outlined how individuals should protect themselves generally from scam communications:
The regulatory body also noted that customers should contact Action Fraud for more information on how to protect themselves against online scams and rip-offs.
It said: “They'll also want to hear from you if you've been contacted by an organisation pretending to be the Fos or another organisation.”
The government is currently working on introducing a ban on cold-callers who try to scam people out of their pension savings.
However, the introduction of such rules are now delayed, since government officials didn’t present the new legislation in Parliament in June, as outlined in the Financial Claims and Guidance Act 2018.