Actor Mark Wahlberg and director Michael Bay are facing legal action over allegations the man who inspired the lead character in their 2013 kidnap comedy Pain & Gain was falsely portrayed onscreen.

The film centred on the true story of a group of bodybuilders who kidnapped and tortured victims and murdered two people in South Florida during the 1990s as part of a sick extortion scheme.

Wealthy businessman Marc Schiller was among those targeted by the Sun Gym Gang members and was held against his will in a warehouse for a month as they attempted to extort money and assets from him.

He was played onscreen by Monk star Tony Shaloub, whose character was renamed Victor Kershaw, but Schiller has taken issue with his depiction on film and in new legal papers, claims he was portrayed as a "deplorable, unlikable, sleazy, rude, abrasive, womanizing braggart" instead of the "family man" he really is.

Schiller insists studio bosses at Paramount Pictures were wrong to market the film as a "true story", instead of making it clear it was only inspired by real-life events, and he is now seeking unspecified damages.

The defendants have yet to respond to the lawsuit allegations, although a disclaimer was included at the end of the movie's credits, stating, "Some names have been changed and certain characters, events and dialogue are fictionalized for the purposes of dramatization."