“Used To Love You” singer Gwen Stefani and country star Blake Shelton apparently have a secret relationship -- and her ex, Bush frontman Gavin Rossdale, isn’t happy about it, Radar Online wrote in an exclusive report Wednesday. The British rocker reportedly thinks his Stefani’s supposed infatuation with Shelton is unbecoming.

Stefani, 46, and Shelton, 38, who are both coaches on NBC’s reality singing show “The Voice,” have not confirmed they’re dating, but Rossdale, 50, was repulsed after photos were taken of them getting close at a party. "It's unflattering for a 46-year old mother of three,”an insider told Radar Online. He is "disgusted that Gwen is acting like a lovestruck teenager." 

Rossedale’s distain for the relationship could due to envy. "There is a lot of jealousy that Gwen has moved on so quickly, and Gavin is very insecure about his career as a musician too," the source said. "Having his wife get involved with a huge star like Blake is certainly a blow to Gavin's ego."

The former couple has joint custody of their children: Kingston, 9; Zuma, 6; and Apollo, 1. After the split, and the Bush singer thinks Stefani’s new relationship could hurt them. Rossdale is "concerned that the kids are going to get very upset if Gwen starts spending a lot of time with Blake so quickly after the divorce," the source said.

Rossdale isn’t the only ex who is upset in this equation: “Little Red Wagon” singer Miranda Lambert is shocked Shelton moved on from their breakup so quickly. “How could she [Lambert] not be just a tad bit jealous? Gwen is absolutely gorgeous and Blake appears to be completely smitten with her,” an insider told Hollywood Life Tuesday. “Miranda could tell by watching them on [The Voice] that they had a certain chemistry… but she never knew it would develop into such a close relationship so fast,” the source added.

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