John Key has shown his disappointment over government spies who illegally bugged Kim Dotcom, yet refused to reveal their motives.

Speaking on TV3's Firstline programme this morning, the Prime Minister was quick to condemn those involved but fell short of explaining their actions.

The public address by Key follows yesterday's revelations of illegal interceptions of information by Government Communications Security Bureau (GCSB) relating to the Dotcom extradition trial.

Key ordered an inquiry into the nation’s secretive intelligence agency after the news, which now threatens to damage the original case against Dotcom.

Speculation suggests the error occurred because security services did not realise Dotcom and his co-accused were New Zealand residents with the GCSB only allowed to investigate foreign intelligence.

Key admitted he did not approve any actions towards the interception of Dotcom's communications, stating the law is clear for all to see.

"What I would say is that I'm very disappointed in the agency, I've made that quite clear," he says.

"I can't stop you from drawing your conclusions but I'd be cautious about drawing those, whether there's any accuracy in them."

In his usual manner, the Megaupload founder took to Twitter to respond to the revelations, tweeting:

"I'm now a real life James Bond villain in a real life political copyright thriller scripted by Hollywood and the White House."

While calling the GCSB "the NZ equivalent of the CIA".

As reported yesterday, Key has assigned inspector-general of Intelligence and Security Paul Neazor to investigate the allegations as Dotcom prepares for his extradition case scheduled for March 2013 over alleged copyright infringement in the U.S.