The Greens believe changes to spy laws will be needed if a new inquiry into the GCSB finds no fault with the spy agency.

The Inspector general of Intelligence and Security is looking into allegations the GCSB illegally spied on New Zealanders while they were travelling and working in the South Pacific.

The government has repeatedly issued denials of wrongdoing, or refused to comment altogether.

Green co-leader Russel Norman says it'd be quite problematic if the inquiry finds the GCSB's actions have been legal.

"If it was found to be lawful for the GCSB to intercept our communications when we're travelling through the South Pacific, and then to feed them into the giant database in the United States, then I think the law would need to be adjusted."

"The Inspector-General will have no option but consider those arguments and the legal status of those arguments, so I think she'll have to reach a conclusion as to whether there's any distinction between mass collection and mass surveillance."

Labour leader Andrew Little says steps will have to be taken if the inspector does find New Zealanders' privacy was invaded.

"If she says it their privacy invaded and it shouldn't have been, then we're going to have to look at what was needed to insure that New Zealanders' privacy interests are properly protected."