Eminem performs onstage at the 2014 MTV Movie Awards in Los Angeles, April 13, 2014. Reuters/Lucy Nicholson

U.S. rapper Eminem’s music publishers have sued New Zealand’s ruling National Party over copyright infringement. The lawsuit, which was filed Tuesday, claimed that the ruling political party used Eminem's song, “Lose Yourself,” for a campaign commercial.

Detroit-based publishers -- Eight Mile Style and Martin Affiliated -- filed the lawsuit in Wellington High Court seeking damages for the use of the 41-year-old rapper’s song for a television commercial for the upcoming election, which is set to begin Sept. 20. The advertisement by the National Party shows some people rowing a boat together to symbolize the party's unity.

"It is both disappointing and sadly ironic that the political party responsible for championing the rights of music publishers in New Zealand ... should itself have so little regard for copyright," Joel Martin, a spokesman for the two publishers, said, according to The Associated Press. "We do not hesitate to take immediate action to protect the integrity of Eminem's works."

However, Prime Minister John Key’s National Party denied the claims stating that it had purchased the music from the Beatbox library and it “was originally published by Spider Cues Music, a well-established Los Angeles-based provider of music to the film and entertainment industry.”

"The National Party completely rejects the allegation that the library music used in its early campaign advertisements is a copyright infringement of any artist's work," the party said, according to AP.

The party reportedly said that it had discontinued the use of the song after Eminem’s publishers complained two weeks ago. “However, this has not satisfied the complainant,” a spokesperson for the party, reportedly said. The political party also added that the music used in the ad has been licensed several times in both Australia and New Zealand with no complaint.

“It appears though that the National Party is the only organization that has used this material that is being legally targeted,” the party reportedly said, in a statement. “As the matter is now before the courts we will not be making any further public comment.”