The firms have not currently been declared in default but are under investigation.

The FSCS is considering whether valid claims for compensation agains the firms exist under its rules.

It wants anyone who invested money through the firms to come forward. It said: “Evidence that former customers provide could be vital for our investigations.”

The FCA has taken action against the firms, alongside six other linked businesses, as they are believed to be a risk to consumers. The other firms mentioned were Cottesmore Associate Ltd, Grosvenor Associates Ltd, Renaissance Advisory Ltd, Falcon Financial Solutions Ltd, Thestral Financial Services Ltd and Semantic Business Services Ltd.

The regulator said that the eight firms appeared to have connections to each other. None have ever been permitted to provide regulated investment services but the FCA said consumers may have invested "substantial sums" with at least two of the firms, Cavendish and Marvell.

The FSCS said it is aware that consumers invested funds into ISAs, convertible bonds and loan notes issued by Cavendish. The investments were made directly through Cavendish Incorporated, through its former appointed representative Cottesmore Associates Ltd, and through Marvell Enterprises. 

However, none of the companies were authorised by the FCA to provide regulated advice on investments.

The credit broker and property developer Marvell Enterprises Limited was declared under investigation by the FSCS in July. Marvell (FRN: 942172) was registered with the FCA from 16 January 2021 as a credit broker but in breach of its permissions was involved in offering products such as an ISA and a high yield bond.

Marvell was first incorporated in July 2019 as a firm buying and selling real estate. It specialised in property development and investment in social housing, student accommodation and commercial property.

Another of the linked businesses the FCA has taken action against – credit broker Renaissance Advisory Ltd of Ilford Essex –was stripped of its Part 4A permission to conduct regulated activities in December 2021.