Rapper Eminem made a rare advertising appearance when Lose Yourself was used in a Chrysler ad, Imported from Detroit, a Wellington judge was told. (File photo)

The National Party's defence of its copyright claim over Eminem's Lose Yourself was "kind of a farce" and should have been settled three years ago, the rapper's copyright manager says.

Speaking from Detroit in the United States, Joel Martin said Eminem would be the main beneficiary of the High Court's award of $600,000 in damages, plus what is probably about $100,000 in interest.

In a 132-page decision released by Justice Helen Cull on Wednesday, the Wellington High Court judge found Eminem's Lose Yourself was a "highly original" work and the "soundalike" version called Eminem Esque, which National used in a campaign advert in 2014, substantially copied it.

MAARTEN HOLL/STUFF Joel Martin, of Detroit, headed the company with copyright authority for Lose Yourself. (File photo)

The similarities between them overwhelmingly supported a finding of copying, the judge said.

READ MORE:

* National Party's ad 'bland' and using Eminem song would never be allowed

* Hard to see what the National Party did wrong in Eminem case, lawyer says

* Any payout for Eminem song breach will have mystery background

* Lose Yourself composer plays guitar riff in court for Eminem song copyright case

"This was kind of a farce, to find out they used Lose Yourself," Martin said. "They should have settled this case three years ago."

NATIONAL The 2014 National Party advert showed a rowing team, with a voice speaking over a Eminem-style music track. (File photo)

It was not until half way through the court hearing earlier this year that they learned, during production, the advert was originally set to Lose Yourself before National sourced Eminem Esque, Martin said.

"One of the defendants just kind of admitted that they replaced Lose Yourself with a weak version of Lose Yourself."

Martin was pleased with the essence of the judge's decision - that she was convinced Eminem Esque was a version of Lose Yourself, even though it wasn't a great version.

MAARTEN HOLL/STUFF Diamond-studded Jeff Bass, one of the composers of the Oscar-winning Eminem song Lose Yourself, leaving court with his wife Julie, after giving evidence at the High Court in Wellington. (File photo)

The damages awarded were not high by US standards, but it made the point that people could not continue to use soundalikes or rip-offs.

"We were looking for more money than that. But at the end of the day I think it's absolutely a reasonable award for New Zealand," Martin said.

"It's a validation to us that this song absolutely is original."

The US parties had suggested damages should have started at US$1 million, about NZ$1.4m.

The National Party had paid $4802 for the licence to use the "soundalike" music library track Eminem Esque, but the copyright holders for Lose Yourself said it was so close to the original that it breached copyright.

Detroit rapper Eminem was not a party to the case. Two United States companies who controlled the copyright sued the National Party and its manager/secretary Greg Hamilton.

National Party president Peter Goodfellow said the result was disappointing.

"The party is now considering the implications of the judgment and the next steps."

It already has a claim against the suppliers and licensors of the track, Goodfellow said.

The judge found although copyright was infringed, the National Party acted after receiving professional, commercial and media advice and was not reckless or "contumelious" of the copyright holder's rights.

The two companies, Eight Mile Style and Martin Affiliated, part-owned the copyright of Lose Yourself and had exclusive rights to bring an action for copyright infringement.

The lawyers for Eight Mile Style, Simpsons Solicitors, said the court decision set a major precedent that would be influential including in Australia and the United Kingdom.

"Eminem Esque clearly stepped over the line. It copied the essential elements that made Lose Yourself a global hit. It was calculated and intentional. Changing a few notes here and there just doesn't cut it," lawyer Adam Simpson said.

Lose Yourself was released in 2002 in conjunction with the movie 8 Mile, and won both Oscar and Grammy awards.

The campaign ads were broadcast more than 100 times before they were replaced because of the copyright complaint.