The Central Bank has issued a warning about investment firm Bernstein, Whitman & Lloyds, which it said had been offering services in Ireland without authorisation.
In its warning the bank notes that it is a criminal offence to operate as an investment firm without its approval and that customers of such firms would not be eligible for compensation funds in the event of a problem.
The Central Bank issues regular warnings about unauthorised firms and maintains a list of such companies on its website.
People with information relating to potentially unauthorised firms are also asked to contact them.
