The English singer/songwriter told CBC News Now host Ian Hanomansing that the similarities with his 2014 hit single Stay With Me and Petty's song were completely coincidental. It was the first time he has talked about the copyright issue.
"It was a complete accident," the soul singer said. "I am 22 years old ... I've never listened to that song."
I Won't Back Down was written by Petty and Jeff Lynne who initiated the copyright dispute due to similarities with Smith's Stay With Me.
Smith said this isn't the first time a new song has turned out to bear close resemblance to one that was published earlier.
'I was very shocked'
"It's a very, very regular thing that happens, and I didn't realize that. And I'm still learning about all this stuff," he said.
"I just go into the studio, and Stay With Me was me just writing a song about me sleeping with too many people, and wishing they would stay over. That was my mindset when I was writing that song, and I was very shocked to find out that the melody was similar, because again, I am 22 and I've never heard the song."
In the end, Smith and his co-writers – James Napier and William Phillips – settled the dispute, accepting the similarities and giving Petty and Lynne writing credits on Stay With Me, along with 12.5 per cent of the royalties from the hit song. Petty and Lynne are also now listed as co-writers on the track.
Petty posted a statement to Facebook saying he held no grudge towards the young singer.
Petty reaches out
"All my years of songwriting have shown me these things can happen," Petty wrote. "Most times you catch it before it gets out the studio door, but in this case it got by."
Smith said Petty also wrote a letter directly to him, reiterating that he understood what had happened, which he thought was really kind.
"It was never a malicious thing," Smith said. "And we [all] tried to deal with it in a very classy way."
On Sunday, Smith heads to the Grammy Awards, where he is nominated in six categories, including Best New Artist and Record of the Year.
"My dreams are complete right now. I literally feel like a winner already and I feel amazing."