Pop star Taylor Swift is being sued for $42m (£27m) for allegedly stealing the lyrics to her hit 2014 song Shake It Off.
US R&B singer Jesse Braham has claimed in legal papers Swift stole the words from a song he wrote in 2013 called Haters Gone Hate.
As well as the monetary compensation, Mr Braham also wants his name added as a writer on the track.
Representatives for Swift have yet to officially comment on the legal case.
Shake It Off topped music charts around the world and reached number two in the UK. The video for the song has been watched more than 1.1 billion times on YouTube.
Mr Braham - who goes by the stage name Jesse Graham - claims he has copyright ownership of the phrases "haters gone hate" and "playas gone play", which appear in the chorus of Swift's song.
In Mr Braham's song, the chorus comprises: "Haters gone hater, playas gone play/ Watch out for them fakers, they'll fake you everyday."
The chorus of Shake It Off features lyrics including: "Cause the players gonna play, play, play, play, play/ And the haters gonna hate, hate, hate, hate, hate." She sings another line: "And the fakers gonna fake, fake, fake, fake, fake."
Apart from the lyrical similarity, the songs bear no resemblance musically.
Mr Braham, 50, told the New York Daily News he believed there was "no way" Swift could have penned the lyrics independently of his song.
"Her hook is the same hook as mine. If I didn't write the song Haters Gone Hate, there wouldn't be a song called Shake It Off," he said.
He added he had spoken to Swift's record label, Big Machine, four or five times about the issue.
He originally asked to be named as a writer and requested a selfie with the pop star, but was repeatedly dismissed and told his claim had no merit.
"At first I was going to let it go, but this song is my song all the way," he said.
It is the second recent legal case involving Swift. Earlier this week the singer filed a counterclaim against a US radio DJ who is suing her over allegations he groped her backstage at a concert in June 2013.
David Mueller said he was fired from his job at KYGO in Denver two days later - but claims one of his superiors committed the alleged assault.
Lawyers for the singer said: "Ms Swift knows exactly who committed the assault - it was Mueller."

BBC