Prime Minister John Key has brushed off Nicky Hager's latest spying allegations, saying no-one in South Korea is interested.
Dirty Politics author Mr Hager alleges the Government Security Communications Bureau (GCSB) was spying on candidates going for the World Trade Organisation's top job.
The investigative journalist claims that while New Zealand Trade Minister Tim Groser was running his failed bid for the WTO's top job in 2013, the GCSB spied on his competitors, including a Korean minister.
Mr Key says no one in Seoul is interested in the accusations which have cast a shadow over the signing of the free trade deal.
"I just had lunch with the Korean president and she didn't raise it, I spent half an hour with her on my own and she didn't raise it," Mr Key said.
"They're not interested in (Edward) Snowden, it's just 2012 backward looking, anti-American bunch of plonkers."
Labour leader Andrew Little says it would be wrong if the GCSB has been used in this way.
"I would have thought it would be unlawful and there needs to be an inquiry to find out and get to the bottom of it," Mr Little said.
But Mr Groser has hinted maybe spying should be expected.
"I assume that everything I say on the phone is capable of being intercepted. Whether it is, and who might be intercepting it, I have no idea," he said.
The free trade deal has taken six long years to negotiate and it means that New Zealand exporters won't have to pay the $229 million in tariffs they do every year. In the first year alone they'll save $65 million.
Mr Key is now setting his sights on Japan where he is hoping to get the Trans-Pacific Partnership (TPP) across the line.