Labour leader Andrew Little does not accept the conclusions in a report that clears the Government Communications Security Bureau's role in supporting the Government's failed bid to install Tim Groser as boss of the World Trade Organisation.
Intelligence and security inspector-general Cheryl Gwyn released the report on Tuesday.
Mr Groser, the then trade minister, was not selected for the third round of the WTO process in April 2013 and ultimately missed out on the job to Brazil's Roberto Azevedo.
Documents leaked by former US National Security Agency contractor Edward Snowden suggested Mr Azevedo and other candidates were spied on by the GCSB during the selection process.
Ms Gwyn's report did not examine detailed actions, such as alleged leaking of documents, but cleared the agency of its broad role in this case.
"The inquiry has found that the GCSB did not act unlawfully or improperly in providing assistance to the New Zealand Government campaign,'' Ms Gwyn said.
She said the Government had made a foreign policy decision to support Mr Groser and had he been selected, he would have advanced the WTO and that would have helped New Zealand's economic wellbeing.
Secondly, under the law at the time, the GCSB had a statutory responsibility to provide foreign intelligence assistance in support of New Zealand's foreign policy objectives.
Mr Little said he did not believe the GCSB's actions met the test of being in the interests of national security.
"The question is whether gathering intelligence for a New Zealand candidate for the head of the WTO is in pursuit of our national security interests - I do not believe it is.''
Ms Gwyn's report said it was for Parliament to decide if contributing to New Zealand's economic wellbeing was a proper statutory objective for the GCSB and the issue had been considered in the recent review of governing legislation.
The GCSB had in place practices and process that provided for assessing the benefits and risks of foreign intelligence activity, "including risk to the GCSB's political neutrality''.
The steps taken in this case were not rigorous but they were adequate.
She said there was now "a standardised process'' with greater transparency.
"I am not commenting publicly on any allegation over particular operational details and it was not necessary for the purposes of my inquiry to confirm or disprove the authenticity of any alleged leaked documents.''
The inspector-general has made three recommendations to strengthen GCSB practices, which the director of the GCSB has accepted.
Her office will monitor their implementation as part of its ongoing review process.
