Blake & Gwen Torn Apart! Why Her Flirtation With A Contestant Crossed The Line

Blake Shelton is NOT cool at all with his “Cool” singer girlfriend Gwen Stefani’s flirty behavior lately – especially when she does it in front of him!

On this week’s episode of NBC’s The Voice, Stefani, 47, flirted with a hunky younger contestant and RadarOnline.com has exclusively learned that Shelton, 40, flipped out backstage!

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The drama started when Stefani was critiquing contestant Chris Blue from Alicia Keys team’s solid performance of singer Miguel’s “Adorn.”

When a flustered Stefani said on-air to Blue, “I don’t know if I was listening to your voice because I was so mesmerized by your body,” the 40-year-old country crooner belted out, “Hey! What the -?”

Although Shelton seemed to be half-joking with his automatic reaction, a show insider revealed that it was a different story after the camera’s stopped rolling!

“Blake is constantly talking about how he thinks that Gwen is too hot for him and when she flirted with the hot younger contestant, he got upset about it and was giving her the cold shoulder afterwards,” the source told Radar.

“You could just tell that there is a lot of tension between the two of them right now. They are not having the same type of interactions that they used to have, on-camera or off-camera.”