Troubled pop star Justin Bieber is jealous over ex-girlfriend Selena Gomez's growing closeness with model Cara Delevingne.

Gomez and Delevingne have apparently become inseparable - they holiday, shop and even shower together.

Gomez has also been linked with dark and brooding Italian businessman Tommy Chiabra, but Bieber is more concerned about his ex-flames growing fondness for the model, reports mirror.co.uk.

"Justin has called Cara on more than one occasion, wanting to know what's going on. It's been clear that he's had a drink beforehand, too," a source said.

The source added that Delevingne, who split from her lesbian lover and actress Michelle Rodriguez last month, has a platonic relationship with Gomez.