Credit: Jean Baptiste Lacroix; Frazer Harrison/Getty

Eddie Cibrian is on the defensive about a tabloid magazine's new report that he's cheating on girlfriend LeAnn Rimes -- with none other than future ex-wife Brandi Glanville.

Cibrian, 37, took to Twitter on Wednesday, blaming Glanville for the new affair story.

"Once again my ex has stooped to a new low attempting  to sabotage my beautiful relationship with LeAnn," the former CSI: Miami actor writes. "Not surprisingly the ONLY magazine that decided to run the story shares the same credibility and delusion as my ex. They should be ashamed of themselves."

Last year, Cibrian's eight-year marriage to Glanville -- they have two young sons -- crumbled after Us Weekly revealed his affair with TV movie costar Rimes, also married at the time. Rimes divorced Dean Sheremet last December; Cibrian filed for divorce from Glanville in August 2009, although it has not yet been finalized.

After going public with their romance in late 2009 Cibrian and Rimes recently moved in together.