The FCA have warned consumers to be especially wary of dealing with unauthorised firms WageAnyDay and PayInSlices (who could be linked to another unauthorised firm iCash UK).
In a statement, they said that the firms are "not authorised by us but have been targeting people in the UK", and could be clone firms.
Websites linked to both firms are no longer active.
The regulator said that almost all firms and individuals carrying out consumer credit activities in the UK must be authorised by them. They are urging consumers to report firms that claim to be authorised but do not appear on the FCA's register.