According to The Sun, the 27-year-old admitted that he could not "promise" fans that he is still single. The paper claims that he and Sarah Robinson have attempted to keep their romance secret, despite reports of their relationship in December.
Asked if he is single, Cardle admitted: "I'm sorry, I can't say that. I can't promise that."
Robinson had written on her Twitter page that she was missing "Sheridan" - the 'When We Collide' singer's middle name.
"Sarah and Matt had a code word so they didn't get rumbled," a source said. "She was worried it wouldn't last because of his career but three months on it's getting stronger."
They are said to have began dating just weeks after Robinson split from her boyfriend of four years Blair Dreelan - a singer with boy band 4th Ba5e who have auditioned for the ITV1 competition three times.
"It seems Sarah swapped an X Factor loser for an X Factor winner," the insider added. "But it's not that simple - with Matt it's the real deal."
It was recently revealed that Cardle has become the first of the show's winners to sign a joint record deal with both Syco and Columbia.