Set to be released by Universal Music this month, the US Sun has now reported the newly recorded duet has already been circulating on social media.
The song titled Hold Me Closer is said to be a mash up of Tiny Dancer mixed with samples from John's other hit songs including the 1992 track, The One with Spears reportedly singing a verse on the remix.
While the song was intended for official release in the coming days, some fans have taken to social media claiming they already have a copy of the single.
In an audio clip a fan posted Twitter, a woman – who is allegedly Spears, can be heard singing "hold me closer Tiny Dancer" amid other lyrics, however the Gimme More singer and John are yet to confirm the leak.
In response to the post many die hard fans of the pop icons have slammed the leak and said it's "not okay".
One fan said, "Why leak it if she's not happy with it?" while another said, "This is not okay. She's working so hard," in reference to the fact that Spears has not released music since her 2016 album, Glory.
However, not everyone was as upset about the leak, one said "OMG I want it." With a second fan tweeting, "she sounds so good".
News of the collaboration first broke in July when a source told Page Six the musicians secretly met in Beverly Hills to record a new version of the beloved 1971 track Tiny Dancer.
It comes after Dua Lipa and Sir Elton John released their hit single Cold Heart. Photo / Getty Images
One source said, "This was Elton's idea, and Britney is a huge fan. They have recorded a remix of Tiny Dancer as a full duet — and it is incredible,"
Adding, "Britney was in the studio in Beverly Hills last week with Elton for the super-secret recording session overseen by uber-producer Andrew Watt."
The source also claimed the single "is going to be the song of the summer," and those who have already heard it said "it is so good".
"Britney is officially back. She's back to work, and she's super excited," they said.
It comes after the Don't Go Breaking My Hear singer collaborated with British pop star Dua Lipa to record the hit Cold Heart, which was a mashup of two of his songs, Rocket Man and Sacrifice.
The song quickly became a fan favourite, reaching the number one spot on the New Zealand music charts, and has been performed by both artists at their respective concerts this year.
