The Poker Face singer and the actor won Best Original Song for their song Shallow from the A Star is Born soundtrack - and performed the song onstage at the 91st annual awards show.
Appearing to invoke their A Star is Born characters, the two looked at each other lovingly as they sang the track while sitting next to one another on the piano.
The performance got a significant amount of attention - especially from those watching and in the audience who felt the chemistry between Cooper and Gaga was undeniable.
However, the 44-year-old actor’s girlfriend Irina Shayk was also in attendance - which prompted Mel B to raise her concerns over the appropriateness of the performance and Lady Gaga’s feelings for her co-star.
Appearing on Good Morning Britain, the Spice Girls singer told Piers Morgan: “See, I felt so uncomfortable for Bradley’s girlfriend, oh my gosh.”
Morgan followed up by asking: “It was the look of love, wasn’t it?” to which Mel replied: “It really was and that’s the whole gossip. That’s the whole thing.
“But I would like to think it was part of the whole performance, because there’s a women’s code and hopefully that’s not… hopefully it’s only professional.”
On social media, the pair’s Oscars duet prompted hundreds of people to question whether the singer and the actor were in love - and whether their relationship explained the end of Lady Gaga’s engagement to Christian Carino.
"Bradley Cooper and Lady Gaga are in love you can't change my mind," one person wrote.
Despite the speculation, video from the awards show appears to show Shayk stand to give the pair a standing ovation following their performance.
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