Katy Perry's ex-lover is jealous of her new romance.

Gym Class Heroes star Travis McCoy, who has had an on/off relationship with the 'I Kissed A Girl' singer for some time, reportedly believes her fledgling relationship with renowned womaniser Russell Brand has no chance of lasting as they are too different.

A source said: "He's livid, but getting a sick kick out of the idea their relationship will go under due to Russell's philandering."

Russell, 34, is famed for his colourful love life. He has admitted being a sex addict and has also battled drug addiction.

Katy, 24, was raised by evangelical Christian parents who run their own missionary outside Los Angeles.

Earlier this week, it was claimed Katy is keen to introduce Russell to her parents, Keith and Mary Hudson, to ally their fears about the new romance.

A source said: "Katy is sure that, after they get used to him, they would approve of Russell, but she wants to get that initial meeting out of the way as early as she can.

"Keith and Mary are devoted to the church and hold the institution of marriage as a central core of their beliefs.

"They are genuinely happy for their daughter, but want to give Russell the once-over."

Katy and Russell were first romantically linked after the MTV Video Music Awards last month when they were seen kissing at Lady GaGa's after-party at New York nightspot Avenue.

They have since enjoyed a romantic holiday to Thailand, and been spotted watching shows at Paris Fashion Week.