The City watchdog has banned the sale of complex unregulated collective investment schemes (UCIS) to ordinary investors.
The schemes promote alternative investments such as traded life policies, fine wines, crops and timber which can offer tempting returns but at great risk to your cash.
The Financial Services Authority has warned that some 85,000 ordinary people that have holdings in UCIS may have been mis-sold them.
Gavin Stewart, the acting director of policy, risk and research at the FSA, said: "Product risks can be much greater on UCIS and expose ordinary investors, for whom these products are clearly unsuitable, to significant potential for large losses on what are esoteric and illiquid investments."
UCIS are not subject to the normal rules that regulated collective investment schemes have to stick to.
The rules mean such investments as unit trusts have safeguards, such as making sure the risk is spread.
But UCIS' greater freedom to pursue unorthodox strategies means that they are only suitable for well-heeled, sophisticated investors who can afford to take the risk - as well as the potential loss.
The FSA has ordered firms to stop selling the schemes to ordinary investors and warned investors to check their suitability of their schemes.
"If customers believe they were mis-sold a product they should contact the firm that arranged it for them and raise their concerns," advised Mr Stewart.
If the customer is not satisfied they can take their complaint to the Financial Ombudsman Service.