Fraudsters have been using BlackRock Fund Managers' name and website as part of a scam.
The FCA has issued a warning after becoming aware of what it described as the 'clone firm'.
The culprits have also been using a version of the name of a genuine employee.
A caller by the name of Harvey Sidhu has been used – a clone of genuinely approved staff member Hardeep "Harvey" Singh.
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The FCA warned on its website: "Fraudsters are using the details of firms we authorise to try to convince people that they work for a genuine, authorised firm.
"Be aware that the scammers may give out other false details or mix these with some correct details of the authorised firm.
"This FCA Authorised Firm that fraudsters are claiming to work for has no association with the 'clone firm'."