The Chartered Institute for Securities and Investment has threatened to take advisers to court if they fraudulently use the Certified Financial Planner designation.
It comes after research from Which found 27 of 43 advice firms on Unbiased - or 63 per cent - claimed to employ certified financial planners but did not have a single adviser with the qualification from the Cisi.
Which did similar research last year and found nearly identical issues with the way advice firms were recording their qualifications, which it warned misled the public.
Kevin Moore, head of business development at the Cisi, said: "If we get to hear of any advisers falsely claiming to hold the Certified Financial Planner designation, or any of our designations, we will investigate this immediately.
"If subsequently we discover the adviser is fraudulently misrepresenting themselves we will take disciplinary or legal action against that individual and this could result in that individual losing their membership of the Cisi.
"We would like to remind all Cisi members and CFP professionals that they are personally responsible for updating all details relevant to their Cisi membership, CFP designation or Accredited Financial Planning Firm status listing on commercial listings websites which they themselves may have paid for and signed up to."
The Cisi operates its own listing service, called Wayfinder, which shows member firms which have achieved AFPF status and financial planners holding the CFP designation.
Which also found seven out of 24 firms falsely claimed to be accredited by the Society of Later Life Advisers and 14 out of 72 claimed to have advisers with chartered financial planner status despite not employing anyone with this credential.
The Cisi said advisers can report people who may be mis-using either the CFP or other designations by emailing firstname.lastname@example.org and providing details of the person in question.