Elton John said Ed Sheeran is a 'f-----g big mouth' for prematurely revealing a secret collaboration.
John told the music outlet NME that he was "sworn to secrecy" about the unreleased song.
Sheeran admitted in an interview with NPO Radio 2 that he initially "didn't feel like [the song] suited me."
British singer Elton John recently used some choice words in reference to Ed Sheeran after the artist leaked the news of a surprise Christmas duet, according to NME.
"I was sworn to secrecy and then big mouth f-----g Sheeran goes to the Netherlands! It's supposed to come out - we haven't finished it yet, so there's still work to be done," John continued. The song currently has no release date or title.
Sheeran previously said the idea for the duet came from John, who called him last year after his song, "Step Into Christmas," landed in the UK Top 10 for the first time.
"Elton rang me on Christmas Day to say Merry Christmas. Elton rings me almost every single day," he told NPO Radio 2.
"He said, 'Step Into Christmas is Number 6 in the charts! I want to do another Christmas song - will you do it with me?" Sheeran continued, according to the outlet.
While Sheeran said he initially "didn't feel like [the song] suited" him, having the opportunity to work on a track with his mentor changed his mind. "It's just me and him. It's great," Sheeran told NPO Radio 2.
Sheeran and John have teamed up before, performing together at the 2013 Grammys. John has also spent time off-stage advising the "Bad Habits" singer under his label Rocket Music Entertainment Group.
In a 2013 interview with Rolling Stone, he said that Sheeran, 30 reminds the artist of himself when first starting out.
"And just the fact that he's got the balls to go and do that in front of 90,000 people - that takes a lot of balls," John told Rolling Stone.
He added, "That takes a lot of confidence. And he has no shortage of confidence."