Jessica Alba's on/off boyfriend CASH WARREN has threatened to sue U.S. tabloid the National Enquirer over a scandalous expose which claims he cheated on the sexy actress with a Russian model. Just weeks after Warren and Alba reconciled, following a summer (07) split, their shaky romance has been hit with a bombshell. Pretty blonde Vera Mishina tells the publication she spent a night partying with Warren in New York, and then a morning making love to the producer - only to discover she was just "a one-night stand" and her lover was already back with his famous ex. The 20-year-old Russian passed a "rigorous" lie detector test before the Enquirer ran with her saucy expose, but that hasn't stopped Warren from threatening to sue. After Mishina gave the publication his cellphone number and a reporter called him to ask for a response to the model's allegations, Warren fumed, "I advise you not to print that if you don't wanna get sued. No comment." But the National Enquirer went ahead with Mishina's story. The model reveals, ""On the night he picked me up and got me into his bed, he was acting like the world's biggest single man. "But I found out that only hours after being with me, he was on a plane back to L.A., where he was then photographed having dinner with her (Alba) and acting affectionate." The spurned model adds, "If he had told me they had gotten back together there's no way I would have allowed him to sleep with me. I now feel like all he wanted was a one-night stand. I feel used. "Cash wasn't very honest to lead me along like he did. Jessica may want to rethink taking him back. He cheated on her the minute he was away from her." Warren has hired a lawyer and denies the story.