A report into standards of behaviour in the Defence Force has identified 30 probable leaks since 1998.
The State Services Commission report has found a small number of army officers are responsible and says there is no systemic problem within defence.
The Chief of Defence Force is vowing to address the issue.
"We have to root it out, sort it out, and get a good clean start early in the new year," Air Marshall Carey Adamson said.
The first major report on problems within defence found 30 probable leaks since 1998, inappropriate behaviour by a small group - mainly army officers - and that most leaks came from two competing factions of the army.
Opposition MPs say the report does not go far enough.
Act MP Rodney Hide wants to see all parties agree that the military are special and should be properly funded.
National's Max Bradford says defence policy should go back to the drawing board to ensure policy is based on the real needs of New Zealand "rather than on an army conspiracy".
The report also says there was a plot to undermine army boss Major General Maurice Dodson because he supported the government's defence policy.
The MP whose files were illegally accessed is pleased with the report.
"I feel totally vindicated because the things that I have been saying....are now there in black and white for the public of New Zealand to see," New Zealand First MP Ron Mark said.
The report authors were unable to find out who was responsible for the leaks, but they say the incoming defence chief must find them and remove or neutralise them. They say his success in the task should be tied to his performance review.
Meanwhile the Defence Minister says he is confident new defence chief Bruce Ferguson will deal with the troublemakers.
"This conduct is absolutely intolerable from this government's point of view," Mark Burton said.
However, this may not be the last of the bad press for the defence force.
Two more reports are still to come - a Queen's Counsel report on the politicisation of the army and a review of defence's organisation and structure.
