John Oliver has taken aim at the New Zealand National Party for its court case against Eminem, in which the group have been accused of ripping off the rapper's iconic hit, Lose Yourself, in a 2014 ad campaign.

The comedian slammed the case as "ridiculous" on the latest episode of Last Week Tonight With John Oliver, which aired in the US just hours ago, saying "it is unquestionably the lamest rap beef since Lil Wayne's five-year feud with William H Macy".

Oliver mocked the fact that the party have denied ripping off Eminem’s 2002 song, despite titling their own track, Eminem-esque'.

"It's true. The track they used is literally called 'Eminem-esque'," Oliver said while fighting back laughter.

"And if you are going to rip off someone else's work, maybe don't include the name of the person you're ripping off."

Footage of Lose Yourself being played in the Wellington High Court was also shown, which Oliver described as "the greatest thing I've ever seen".

"Some define comedy as tragedy plus time, but for me, the purest definition is a middle-aged Kiwi in a robe playing Eminem's Lose Yourself to a completely silent and motionless court room."

Check out the full takedown in the clip below.

The episode will air in Australia tonight at 9pm on the Comedy Channel.