"Real Housewives of Potomac" star, Michael Darby is taking Candiace Dillard Bassett to court for defamation ... after she claimed he offered up cash to have sexual relations with another man.
According to legal docs, obtained by TMZ, Ashley Darby's hubby is suing Candiace over comments she made during the latest season of the reality series -- where she didn't hold back during one of her many arguments with Ashley.
On the show, Candiace tells Ashley, "Your husband likes to leave you and go to a man named [censored]'s house and suck his ****." She never says who the guy is, but Candiace later claimed Michael paid for sex.
Michael's calling BS on all of it ... adding he sent her a cease and desist earlier this year regarding her comments -- but claims she has yet to retract any of her allegations.
He wants $2 mil in damages to make things right.
Fans of the show know Candiace and the Darbys have had long-standing beef ... with her calling Michael and Ashley out numerous times. Looks like the latest incident took things too far, though ... at least according to Michael.
We reached out to reps for Candiace ... so far, no word back.