The couple fell for each other when they shared the I'm A Celebrity jungle together in November last year. They were torn apart when Marc was voted out of the programme, but once the show was over, the pair declared that they were "in love" and even discussed having children.
However, pals have now revealed that Cerys got bored of the relationship and dumped Marc by phone two days before Valentine's Day. She now wishes to focus on her music career.
"The passion fizzled out and they've hardly seen each other in the last month. All the talk of having babies and settling down turned to dust," a source told the Sunday Mirror. "She realised the relationship was going nowhere and wants to concentrate on her tour, so she told Marc they were finished this week."
Marc's mother Dolores Noronha confirmed: "It's finished with Cerys. He's very upset, very down."
In an interview at the end of last year, Cerys' ex-boyfriend Seth Riddle warned: "She rushes into everything - she did the same thing with me. She's the sort of person who's prone to changing her mind a lot."