Labour leader Andrew Little says John Key needs to be clear with New Zealanders about what the difference is between the collection of their data versus surveillance by the GCSB.
The Prime Minister says he will resign if the GCSB has undertaken mass surveillance against New Zealanders, but not if it has undertaken mass collection of their communications.
Mr Key has repeated that the GCSB is not and never has undertaken mass surveillance of New Zealanders.
He says everyone can have their own legal definitions of mass surveillance. "But I think it's pretty clear what we mean by mass surveillance - the entire population or at least a big part thereof. Everyone I think understands what surveillance is. And that is against the law."
Mr Key said: "I didn't even know what you mean by mass collection. I have no clue. It is not a term I have ever seen. It's not a term I have ever used. It's not something that sits in something I see."
Mr Little says he thinks the Prime Minister is being "pretty tricky" about the difference between data collection and surveillance.
"I think he needs to be clear with New Zealanders about what that difference is. He says that you can go to a different lawyer and get a different opinion.
"He's got the country's top lawyer, the Attorney-General, in charge of the security agencies. He can ask his top lawyer and tell the rest of New Zealand what the data collection is and whether or not that's surveillance."
Mr Little says his view is that once the data is collected that's the intrusion of privacy.
"It's like nicking someone's mail. You might not open it but you've got their mail. That's the intrusion on the person's privacy," he says.
"It's the same here. He should be clear with New Zealanders about whether that's what's happening and if so he's got to think about what he does," Mr Little says.