Jennifer Lopez and Casper Smart are upset with Star and In Touch magazine for posting stories claiming that Casper Smart is gay. We ran the first gay rumor in June and today Star magazine 'reported' that Casper gets hand jobs from a gay sex club.

Jen and Casper's attorneys sent letters to Star and In Touch warning that their rumors are "false, malicious and defamatory" and will cause "immense damage" to the couple's reputations and careers.

Star magazine reported that Casper was photographed outside a XXX peep show in New York that's a "well-known cruising spot for gay men looking for instant hookups."

The couple's lawyers have each demanded the mags print a full retraction … warning Smart and Lopez will "immediately file a lawsuit" if the magazines fail to do so.