WELLINGTON (AFP) - New Zealand's ruling National Party is being sued for alleged unauthorised use of rapper Eminem's song Lose Yourself in campaign ads ahead of next Saturday's general election.

Detroit-based Eminem Publishers said in a statement Tuesday it had started court proceedings in New Zealand.

"The proceedings stem from allegations that unauthorised use has been made of Eminem's Grammy and Academy Award winning song, Lose Yourself, in election campaign advertising run by the National Party," the statement said.

Lawyer Garry Williams told Fairfax Media it was the owners of the song, not Eminem, taking the action.

The National Party said in a statement it rejected the allegation, saying it purchased the music from a recognised production music supplier and was assured it did not infringe any copyright and was an original work.

"We note that the work in question has been licensed multiple times both in Australia and New Zealand without issue or complaint," the statement said, referring to three television programmes it had been used on.

"The National Party will be defending this action vigorously."