To call one of hip-hop's kings "unoriginal" is quite a statement.

But according to New Zealand Radio, that's what Eminem's music publisher, Eight Mile Style, was told in the High Court in Wellington, during one of the closing arguments in their ongoing copyright trial with the National Party.

Eight Mile Style is claiming music used in a 2014 election campaign was all-too-similar to the hit song 'Lose Yourself'. Described as "Eminem Esque" by a music production library, $4802 was paid for use the track featured in the campaign.

National Party lawyer Greg Arthur said that, to have breached copyright, the track must have lifted a "substantial part" of the original source material. Said Arthur, "Determining infringement is not a question of note for note comparison, but whether the substance of the original copyright work is taken."

Mr Arthur also iterated that the basic musical core of Eminem's song is not original, adding that evidence previously given at the trial by one of the track's creators Jeff Bass, had admitted to the borrowing of material from other musicians.

The lawyer for Eight Mile Style is scheduled to make his closing argument tomorrow.