Ed Sheeran is being sued for $20 million for allegedly copying a song released by X Factor winner Matt Cardle.

A lawsuit filed in a Los Angeles federal court claims Sheeran's 2014 summer hit Photograph infringes the copyright of Cardle's 2012 single Amazing.

Lawyer Richard Busch, who recently triumphed on behalf of Marvin Gaye's family in a copyright case over the Robin Thicke hit Blurred Lines, is representing Amazing's songwriters Martin Harrington and Thomas Leonard.

The songs’ similarities “reach the very essence of the work”, the lawsuit reads.

"The similarities go beyond substantial, which is itself sufficient to establish copyright infringement, and are in fact striking. The similarity of words, vocal style, vocal melody, melody and rhythm are clear indicators, among other things, that Photograph copies Amazing."

According to court papers posted online, the lawsuit alleges that the choruses of Amazing and Photograph share 39 identical notes.

Sheeran will have to answer the charges alongside his Photograph co-writer, Snow Patrol's Johnny McDaid, as well as other co-defendants including Sony/ATV Songs, Warner Music and Polar Patrol Music Publishing.

Cardle, who won the ITV talent show in 2010, is not a party to the lawsuit.