‘The X Factor’s’ L.A. Reid On Letting Lady Gaga Slip Away: ‘It Was The Worst Thing I’ve Ever Done’

He’s signed pop superstars Usher, Pink, Justin Bieber and Rihanna, but music mogul and “The X Factor” judge L.A. Reid says there’s one monstrous artist he regrets letting slip through the cracks.

“This artist came to my office… she played piano, she had on white go-go boots – like, all the way up to here, thigh high boots — she sat down at that piano, she played and she sang,” L.A. told Access Hollywood’s Shaun Robinson during a new interview in Los Angeles on Tuesday. “When she was done, I said, ‘You are an amazing artist, a true star, and you will change music,’ and I signed her. Her name was Lady Gaga.

“Then, a few months later, I got her demos, and it was a work in progress, and I was having a bad day. I’m telling you, I was having a bad day,” he continued. “And I said, ‘You know what? I really don’t like it. Let her have her freedom, let her go find her career.’ It was the worst thing I’ve ever done.”

Though the former Island Def Jam Music Group chairman still regrets his decision to release the “You and I” singer, the discovery of a then-unknown Canadian teen helped to cushion the blow.

“I felt bad, but I swear to you, like a month later Justin Bieber came and redeemed me, so, you know, I survived it all,” L.A. told Shaun, of signing the then-14-year-old “Baby” singer shortly after sending Lady Gaga packing. “But I’m a little bit jealous, because the Twitter following, for example, the biggest ones are Bieber and Lady Gaga, so I would have felt like the king of the world! Instead I felt like half the king.”

Catch L.A. in action, along with Simon Cowell, Paula Abdul and Nicole Scherzinger, on “The X Factor” – Wednesdays and Thursdays on FOX.