Prime Minister John Key will not confirm or deny the latest allegations about the Government's spy agency.
Journalist Nicky Hager said he has evidence New Zealand spied on candidates vying to lead the World Trade Organisation, in a bid to help the New Zealand contender Tim Groser.
Mr Key said previous claims made by Mr Hager had been based on old or out-of-date information, or were simply wrong.
"There are many reasons why we may or may not undertake information that we gather.
"We have an intelligence agency and we don't deny that we actually use them to gather intelligence, and there's a wide range of reasons for that."
Mr Key said the GCSB was acting within the law.
Mr Key repeatedly said he would not talk about individual investigations by the GCSB, but Andrew Little said Mr Key is picking and choosing.
"Well they've discussed security matters before when it comes to [Islamic State] and terror threats.
"Our security agencies are there to deal with security threats to New Zealand, not advance the career interests of politicians," Mr Little said.
Mr Little said he would ask the Inspector General of Intelligence and Security to investigate the new claims.
"It's outrageous. The GCSB is not there to advance the careers of certain individuals, it's there to address and deal with security threats to New Zealand."
Mr Key was asked about the Inspector General holding an inquiry.
"What do you mean an inquiry? Don't you understand their job? She goes out there and she has a permanent thorough 100 percent, 24-hour-seven capacity to look at anything and everything, and does.
"She looks at every single warrant that we do, she goes and looks at all of the activity, she has seven staff - this isn't some random organisation that just sits out there doing what the hell it likes."
A spokeperson for Chris Finlayson, the Minister responsible for the GCSB, said he did not comment on speculation about GCSB matters that may or may not be operational.
Green Party MP Kennedy Graham questioned whether the Government used the GCSB to spy on other countries vying for a seat on the UN Security Council.
"The suggestion would be from this new revelation is that it was," said Mr Graham.
"So I think the Prime Minister needs to make a clear statement to the New Zealand public reassuring us all that the GCSB is not engaging and has not engaged in that kind of undertaking, because it goes way beyond the legitimate role of the GCSB."