Q. How do you get your own back on estate agents? A. Make them the villians in CSI

A married couple are suing the makers of CSI: Crime Scene Investigation, claiming that a writer of the hit TV series deliberately named two shady, sex-obsessed characters after them in revenge for a home sale that fell through.

Estate agents Scott and Melinda Tamkin want $6m (£3.75m) for defamation and invasion of privacy, after their names were given to a fictional pair of bondage-loving property entrepreneurs in a CSI episode entitled "Deep Fried and Minty Fresh".

In a lawsuit filed at LA County Superior Court this week, the husband and wife duo recall how they fell out with Sarah Goldfinger, a writer and producer responsible for that episode of the series, after she tried, and failed, to buy a house from one of their clients in 2005.

Goldfinger later attempted to publicly humiliate them, the couple claim, by "creating from whole cloth" characters named after them, who "engaged in a reckless lifestyle of sexual bondage, pornography, drunkenness, marital discord, depression, financial straits and possibly even murder".

The CSI episode in question, which aired in February, sees police forensics experts investigate whether the recently deceased Melinda died at the hands of her husband Scott, a mortgage broker who drinks heavily and spends most of his free time watching violent pornography.

Goldfinger gave the fictional couple the surnames Tamkin in both her script and synopses of the episode that were posted online, the lawsuit claims. She also stands accused of telling casting agents to send dark-haired actors who resembled the real-life couple to auditions for the roles.

The Tamkins, whose website touts their "hard work, honesty and ethics", say they first found out about the smear when Scott "Googled" his own name, and stumbled upon several CSI "spoiler" sites. He was particularly shocked to see pages discussing the fictional couple's kinky sex practices, many of which carried links to pornographic websites.

CBS, the show's broadcaster, immediately agreed to remove the plot synopses when Scott contacted them. They also agreed to have the characters' surname changed to "Tucker" in the version of the show that was finally broadcast.

However, a lawyer for the couple, who have three children and specialise in selling eco-friendly family homes in upmarket areas of Southern California, told the Los Angeles Times that the damage had already been done, since "spoiler" sites had carried the original names for five months. The "11th hour" change was "for all intents and purposes an admission that [Goldfinger] had stepped over the line".

Any potential client who did an internet search for the Tamkins' real estate company during the intervening period and came upon the description of the characters in the CSI synopsis would have been "highly unlikely" to "ever have contacted them and wanted to retain them as a professional real estate agent", claimed the lawyer, Anthony Glassman. "In this business, you never know why the phone doesn't ring."

The lawsuit, which was lodged on Friday, names a host of defendants, including Sarah Goldfinger and CBS, along with Jerry Bruckheimer, the Hollywood action movie impresario whose firm produces CSI, and Goldman Sachs, the finance company which bankrolled the episode in question.

None of the accused parties have yet commented on the case. However the extraordinary success of the CSI franchise means that whatever their defence, it will be difficult for them to play down the potential reach of the episode in question.

CSI, which follows police forensics teams investigating murders, is set in Las Vegas, with spin-off versions in New York and Miami. The three shows reach 50 million people in the US each week, and are syndicated to 200 countries, with a total audience estimated at two billion.

The phenomenal success of the show, which has been criticised for some of its violent and sexual themes, means there are hundreds of fan sites dedicated to the show, many of which carry detailed debates about the real-life crime stories and characters who have inspired each episode.

Goldfinger has worked on CSI since 2003, three years after it launched, and met the Tamkins in 2005 when they were representing the owners of a home in west Los Angeles that she was attempting to buy.

Glassman said that Goldfinger pulled out of the deal during "escrow", when a deposit has been paid but contract negotiations are typically still ongoing. However he said their business dealings were "just a normal interaction between potential buyer of a home and a real estate agent representing a seller".