The man, who has not been named by French authorities, was considered the mastermind of a swindle in which €1.66 million euros in loans were fraudulently obtained from French banks by British nationals.
The 38-year-old was arrested on May 14 and appeared before a judge on Friday on suspicion of organised fraud along with a French national, in the Poitiers Vivonne prison in the west of France.
According to French radio RTL the man had been identified as a potential suicide risk. Nevertheless he was found hanging in his cell on Tuesday. An official investigation has been opened by authorities.
According to RTL the victim left two suicide notes, the contents of which have not been made public.
Several other suspects, believed to have been involved in the scam, including other British nationals, are due to go before a French judge at a later date.
A spokeswoman for the British Embassy told The Local: “We are aware of the death of a British national in France on May 21st and we stand ready to provide consular assistance.”