The man took paying passengers on 20 work trips between the towns of Bordeaux and Nantes over a three-year period using his company car, according to reports.
They travelled using the French carpooling service BlaBlaCar, which allows motorists to cover their driving costs and passengers to travel cheaply between destinations.
When the man's bosses found out, they promptly fired the Frenchman, who had been employed by the consultancy firm since 1999.
The man claims that he donated all the proceedings - a total of €610 - to two charities, Clowns Stéthoscopes and Surf Rider.
"It's more logical to have three or four people on these journeys rather than just one," the man told the Ouest-France newspaper.
The man's trips between Bordeaux and Nantes would have taken over three hours, at a distance of around 350 km. Photo: GoogleMaps
When the man's lawyer noted that nowhere in the man's contract did it forbid carpooling, the company's lawyer responded:
"Yes, but it doesn't say anywhere that you can't hit your colleagues. It's just obvious," reported the paper.
The man's lawyer smelled foul play, however, noting that the man had been using BlaBlaCar, with a totally public profile that featured his full identity, for three years - but was fired seemingly overnight.
He suspected that the real reason the man lost his job is because he had applied for a position on the staff representative board, a move which displeased the firm for some reason.
The former employee is seeking over €80,000 in damages, and over €250,000 in lost salary.
A verdict is expected in July.
A spokesperson from BlaBlaCar said that the company's rules don't expressly forbid people from using company cars on the service.
"Our message is all about saving costs, you can't make any profits on BlaBlaCar, that's the whole point," spokesperson Kevin Deniau told The Local.
He explained, however, that the terms and conditions do encourage people to check with their employers before signing up a company car to the service.