Revelations that MPs' emails are being screened, and even blocked, has sparked an investigation at Parliament.
Labour made the discovery when MP Chris Hipkins tried to send information to a journalist on Monday night.
But it was blocked, because Parliamentary Service found it contained "sensitive words".
"It was blocked and I was not able to send it because the document that I was attaching, that I had obtained under the Official Information Act, previously had a government security classification," he said.
Mr Hipkins said they have no right to screen emails sent by Members of Parliament, and he's now realised how widespread it is.