The FCA has launched an investigation into mini-bond provider London Capital and Finance over concerns about the way it markets products.
LCF has also been told to cease all regulated activity and may not deal in any way with its assets including the money held in its banks accounts.
On 13 December the watchdog announced it had directed LCF to withdraw all of its existing marketing materials in relation to its fixed rate Isa or bond.
LCF is the issuer of mini-bonds it states it uses to make loans to corporate borrowers to provide capital for further investment.
The FCA estimates there are approximately 14,000 customers invested in LCF bonds and says its enforcement division is conducting the investigation.
A mini-bond is an unlisted debt security, typically issued by small businesses to raise funds.
The regulator points out issuing mini-bonds is not a regulated activity, so firms issuing mini-bonds do not need to be authorised by the FCA.
However it also says when an authorised firm approves a promotion for mini-bonds, they must ensure that it is in line with FCA rules, and that the financial promotion is fair, clear and not misleading.
This means, for example, that risks are appropriately communicated.