The Inspector-General of Intelligence and Security, Cheryl Gwyn, has confirmed she has called a number of people to give evidence under oath to her inquiry into the release of spy agency information to a blogger.
The investigation relates to the release of a Security Intelligence Service (SIS) briefing prepared for the-then Labour leader, Phil Goff, in 2011 to blogger Cameron Slater. It will look into allegations the documents were declassified in order to be used politically.
In an unusual move Ms Gwyn has given an update of her investigation, saying the inquiry would be conducted in private.
She said individuals would be questioned separately over a period of more than a week.
Under the summons they must turn up for the interviews or face a fine of up to $5000. They must also present documents or other material the interview if they are required.
Ms Gwyn said the inquiry was a significant one and involved access to a variety of IT systems, documents, phone records and other information.
She said she would not be cutting corners and was not able to say how long the inquiry would take.
Former Labour Party leader Phil Goff has called for John Key to be questioned under oath at the inquiry.
As yet unnamed staff from the Prime Minister's office have seen summoned but not John Key personally, though he has said he would be happy to give evidence.
Mr Goff said he would be questioned next week, and believes Mr Key should be there too.
"Why shouldn't Mr Key be giving evidence to this, because he is at the heart of the issue as to what information was given to Cameron Slater that led to his making the request, and why he brought this issue into the political arena in the first instance."
The SIS documents released to Mr Slater in 2011 appeared to contradict Mr Goff's claim that he hadn't been briefed on matter of national security. Mr Goff continues to maintain he wasn't briefed.