There are calls for Tim Groser to be prepared to fall on his sword if an investigation into the GCSB goes against him.

The Inspector-General of Intelligence and Security is looking into allegations New Zealand's spy agency - the Government Communication Security Bureau - used an internet surveillance system to spy on candidates for head of the World Trade Organisation.

Trade Minister Tim Groser was running for the job against candidates from Mexico, Brazil, Jordan, Kenya, and elsewhere. He was unsuccessful.

The New Zealand Herald revealed the scandal based on documents provided by whistleblower Edward Snowden.

The minister in charge of the GCSB at the time was Prime Minister John Key.

Greens co-leader Metiria Turei believes the allegations are significant.

"It should lead to Tim Groser potentially losing his job over this," she said. "If proved true this is a serious abuse of power."

Labour leader Andrew Little says he cannot see spying on job candidates "possibly fits the mandate for the GCSB."

"If the GCSB is being used to further individual interests it would be totally and utterly wrong."

When asked to comment on the matter yesterday, Groser's office refused to grant an interview, or make a statement.

Inspector-General Cheryl Gwyn said the activity of the GCSB gathering foreign intelligence is of sufficient importance for the inquiry.

Gwyn said while it's unlikely she'll be able to confirm or deny specific spy allegations, she can look at the GCSB's activities and whether they worked within their mandate, and whether spies maintained their political neutrality.