Prime Minister John Key says he would not resign if it is proved that the GCSB carries out mass collection of New Zealanders' communications.

John Key addresses press conference. Source: 1 NEWS

Mr Key has always insisted he would quit if it was proved that New Zealanders were subject to mass surveillance.

He insists the GCSB has told him that it is not capable of doing mass surveillance and is not legally allowed to do it.

Late last week former GCSB boss Sir Bruce Ferguson told Radio New Zealand that there was mass collection of New Zealanders' data as part of spying operations in the Pacific.

Sir Bruce also maintained however that it was legal as it was collected inadvertently and that the information on Kiwis was not used.

When asked today about whether there was a difference between the terms "collection" and "surveillance", Mr Key responded by saying he was "sure the lawyers would tell you there is a difference".