Girardet, whose family founded the renowned Hôtel de Ville restaurant in Crissier near Lausanne, filed a complaint with Valais justice authorities last year against an investment manager identified as Sébastien B., the broadcaster said on its news website.
Girardet had entrusted the accused with the management of part of his fortune.
Sébastien B. reportedly sent the star chef false bank documents indicating that he had a balance of 3.5 million francs at the end of 2014.
However, when Girardet checked with the bank himself he discovered the balance was only 830,000 francs, RTS said.
Contacted by the broadcaster, the chef confirmed that he filed a complaint but declined further comment.
Bilan business magazine recently reported that Benoît Violier, the chef who took over the Hôtel de Ville restaurant, committed suicide February 1st because of financial problems linked to the same financial adviser.
However, the report has been denied by Violier's wife, Brigitte, and others close to the chef, whose restaurant in December was named best in the world by La Liste, compiled by the French government.
Nonetheless, the RTS report said that Sébastien B. knew Violier and was a regular customer at the Hôtel de Ville, where he organized tastings of rare wines.
He even celebrated his 40th birthday at the restaurant, when Girardet, Violier and the Hôtel de Ville's previous chef, Philippe Rochat, cooked dishes for the occasion, the report said.
But following complaints from a dozen people, Sébastien B. was arrested last July and taken into preventive detention until he was released in January, RTS said.
The Valais prosecutor's office is not commenting on the case other than to say that the investigation is continuing and will likely take months if not years to conclude.
In another report on Sunday, RTS described Sébastien B. as a smooth talking, charismatic man who who was able to charm his clients, older, wealthy people apparently eager to sink money into his investment schemes.
These included a plan to acquire 1,500 rare bottles of Burgundy wine, and another to invest in a Dutch startup, both investments promising lucrative returns, the report said.