The PIA is believed to be considering an investigation into Manek Investments, the company set up by Sunday Times fantasy fund management winner Jayesh Manek.
Reports suggest the regulator is examining the advertising of the Manek growth unit trust but the PIA refuses to confirm whether there is an investigation. Manek growth has raised more than £90m since December.
A spokesman for Manek Investments says: "We are not aware of any probe into the adverts." He adds that the PIA was shown several of the ads before they were published.