Katy Perry,
The Katy Perry Dark Horse music video has been criticized by religious groups. YouTube

Katy Perry has been hit with a multi-million lawsuit after allegedly plagiarising a Christian rap song for her recent hit, Dark Horse.

Flame, a rapper from Louis, Missouri, alleges that the pop star used the melody from his 2008 song Joyful Noise without his permission.

The suit filed by producers Chike Ojukwu, Lecrae Moore and Emmanuel Lambert along with Flame claims that although the snap-based beat and high-pitched techno melody were slowed down on Dark Horse, the similarities between the two tracks are obvious.

"When they're separated, they seem a bit different, but when you bring them to the same tempo and you just change her pitch down one octave, they're identical... When things are that similar, it's hard to dispute," DJ Cho'zyn told Rapzilla.

Flame, whose real name is Marcus T. Gray, was nominated for a Gospel Music Association Dove Award for Joyful Noise, while its album Our World: Redeemed earned a Grammy nomination.

The gospel star insists that the religious ode has been "irreparably tarnished by its association with the witchcraft, paganism, black magic and Illuminati imagery evoked by the same music in Dark Horse".

This is not the first time Dark Horse has provoked controversy. Following its release in 2013, religious groups labelled the accompanying music video "blasphemous" and accused the 29-year-old diva of being disrespectful.

Perry, whose parents were Pentecostal pastors, has distanced herself from her Christian upbringing in recent years.

The I Kissed A Girl hitmaker's latest material is worlds away from her 2000 debut album - titled Katy Hudson – which was a Christian rock and gospel record with tracks like Faith Won't Fail.

Perry has not commented on the plagiarism lawsuit.