Asked about the case today, Prime Minister Bill English said he was unable to comment.
"That is a matter for the courts, they are dealing with it ... so I don't have any comment to make on it. I've had no contact with anyone related to the court case."
National Party president Peter Goodfellow has been contacted for comment.
WATCH: JOHN OLIVER DISCUSSES EMINEM V NATIONAL PARTY
In September 2014, spokesman for the publishers Joel Martin said Eminem was never approached for permission to use his work in National's rowing-themed election ads, which featured backing music similar to the riff of Lose Yourself.
"It is disappointing and sadly ironic that the political party responsible for championing the rights of music publishers in New Zealand by the introduction of the three strikes copyright reforms should itself have so little regard for copyright," Martin said at the time.
The National Party said the music came from an Australian-based production outfit and it had been used by others without complaint.