The Financial Services Authority will launch an online register of authorised firms on 29 April.
The Central Register website will enable the public to carry out basic authorisation checks on firms they are thinking of dealing with.
Being authorised means that a firm meets the regulator's standards of honesty, financial soundness and competence and offers safeguards if something goes wrong.
FSA director of authorisation David Kenmir: "It is vitally important that consumers do not put themselves at risk by dealing with an unauthorised firm. Checking a firm's status before you invest with them is a good way to avoid the cowboys."
He adds: "By making the Central Register available over the internet, the FSA is taking an important step towards meeting its objectives of promoting public understanding of the financial system."