The FSA is contacting over 75,000 people to warn them they are at risk of being targeted by fraudsters.
Their names were found on lists gathered from firms the regulator believes were fraudulently selling investments in land or worthless or fake shares.
The list of 76,732 represents the largest number of possible victims the FSA has ever contacted at once. It says most people will receive letters but had only email addresses for 19,101 cases.
FSA head of unauthorised business Jonathan Phelan says: “If you get a letter or email from the FSA over the next five or six weeks, please read it, it could save you tens of thousands of pounds. If you have already been contacted by a firm offering you a ‘once in a lifetime’ investment opportunity or have already invested, then tell us. The information you have could help us catch criminals and shut down their scams.”