Katy Perry and Diplo have teamed up for a Taylor Swift diss track.

The former lovers have reportedly got together in the studio and bonded once again over their mutual hatred of the 'Shake It Off' singer by penning a track titled 'Crocodile Tears'.

A source revealed: ''Katy knew Diplo would be just the man to produce 'Crocodile Tears' for her and has now registered it.''

The song is expected to be a retaliation against Taylor's scathing hit 'Bad Blood' which took aim at Katy, who Taylor once described as her ''straight-up enemy''.

Diplo has previously spoken about his dislike of the star, which led him to back a campaign to get the singer ''a booty''.

Up until now, both Taylor and Katy have not specifically mentioned each other's names in their mysterious feud but while the 'California Gurls' singer has remained largely quiet on the subject, she feels now is a good time to give her side of the story.

The source continued: ''So far she's been very restrained with what she's said about Taylor in public but is now finally ready to put her side across via the song - which is all about being fake.''

And although it remains unclear whether the track will feature on the follow-up to the 30-year-old singer's 2013 album 'Prism', she has vowed to release it at some point.

The source told The Sun newspaper: ''It isn't yet known whether it would be released as a one-off or as part of Katy's fourth album, but she is keen for fans to hear it.''