Kim Dotcom, founder of Megaupload, has suffered another setback in his legal entanglements.

The New Zealand Supreme Court denied his appeal to access the evidence the US feds have on him that will be used to extradite him back to the US.

"The Supreme Court has decided by a majority… that the District Court was wrong to order disclosure by the United States of the documents concerned," the highest court said today.

Dotcom and three of his Megaupload colleagues face extradition over these charges: copyright infringement, money laundering and racketeering.

Although Dotcom and his co-accused deny any wrongdoing, US authorities claim that the online file-sharing service cost film studios and record labels more than $500m while it raked in more than $175m itself in revenues.