"Some of our staff have actually been emailing me with other examples of where their emails have also been blocked.
"They're all recent examples, like within the last few weeks. So I'm not sure how far back this goes.
"This is a very serious matter because it doesn't matter how I came to hold the document, the fact that the Parliamentary Service are monitoring the emails coming to and from MPs' email addresses is completely unacceptable."
The Parliamentary Service manages parliament and its communications systems.
Speaker David Carter is responsible for it.
He said he would look into Mr Hipkins' complaint and report to Parliament on Wednesday.
-Additional reporting by NZ Newswire