The FCA introduced the ban without consultation in January following concerns that speculative mini-bonds were being promoted to retail investors who neither understood the risks involved, nor could afford the potential financial losses.

In introducing the rules permanently, the FCA is proposing a small number of changes and clarifications to the ban introduced in January. This includes bringing listed bonds with similar features to speculative illiquid securities and which are not regularly traded within the scope of the ban.

Sheldon Mills, interim executive director of strategy and competition at the FCA, said: “We know that investing in these types of products can lead to unexpected and significant loses for investors. We have already taken a wide range of action in order to protect consumers and by making the ban permanent we aim to prevent people investing in complex, high risk products which are often designed to be hard to understand.

“Since we introduced the marketing ban we have seen evidence that firms are promoting other types of bonds which are not regularly traded to retail investors. We are very concerned about this and so we have proposed extending the scope of the ban.”

The term mini-bond refers to a range of investments. The ban will apply to the most complex and opaque arrangements where the funds raised are used to lend to a third party, or to buy or acquire investments, or to buy or fund the construction of property.

There are various exemptions including for listed bonds which are regularly traded, companies which raise funds for their own commercial or industrial activities, and products which fund a single UK income-generating property investment.

The FCA ban will mean that products caught by the rules can only be promoted to investors that firms know are sophisticated or high net worth. Marketing material produced or approved by an authorised firm will also have to include a specific risk warning and disclose any costs or payments to third parties that are deducted from the money raised from investors.

The watchdog has limited powers over the issuers of speculative mini-bonds who are usually unauthorised but can take action when an authorised firm approves or communicates a financial promotion, or directly advises on or sells, these products.