Eddie Cibrian and LeAnn Rimes. (WENN.COM)

Actor Eddie Cibrian has been exposed as a serial cheater by the model he was dating behind his wife and mistress LeAnn Rimes’ back.

Pretty Scheana Marie Jancan has sensationally claimed she was part of a love square, which ended the TV star's marriage to Brandi Glanville - and she's still in shock about the whole thing.

Jancan tells America's Life & Style magazine she and Cibrian were romantically involved for three years during his marriage, but she had no idea he was cheating on her with country star and actress Rimes.

The two co-stars initially denied reports they were an item after surveillance cameras caught them enjoying an intimate night out together, but Rimes and Cibrian, who played lovers on TV movie Northern Lights, have since ended their marriages and gone public with their love for each other.

Jilted Jancan has warned Rimes to be careful - because she's sure her ex-lover will cheat again.

She tells the publication, "Eddie's with LeAnn now, but it's just a fling. Eddie cheated on Brandi. He cheated on me. He's going to do it to LeAnn."

The bitter model still can't believe she lost out on love to the Blue singer: "I knew they were co-stars, and I didn't notice much chemistry between them in the movie."

And she's still desperate to find closure: "He's (Cibrian) still never given me a 'Sorry, we're done'. He hasn't ended it with me."

The actor has ended his eight year marriage to Glanville, the mother of his two sons.