The Parliamentary Service is refusing to comment on claims by Labour MP Chris Hipkins it intercepted and blocked an email he tried to send to a journalist.

Parliament is defending its computer security that is screening and blocking MPs emails if they contain words like "sensitive" or "classified".

An urgent investigation has being called for by Labour's Chris Hipkins after an email he was trying to send to a Fairfax journalist was blocked on Monday night.

In an email exchange between Hipkins and Parliamentary Service, which provides administrative and support services to MPs, Labour's chief whip was told his email was blocked because it had "trigger" words in it.

INTHEHOUSENZ/YouTube Labour MP Chris Hipkins has questioned Parliament's email monitoring after an email he tried to send to a journalist was blocked.

The Speaker of the House, David Carter, is waiting on a report from Parliamentary Service about the matter and told MPs he would come back with a response on Wednesday.

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CAMERON BURNELL/STUFF Labour's Chris Hipkins had an email to a Fairfax journalist blocked by Parliamentary Service on Monday.

﻿Parliamentary Service told Hipkins the email he tried to forward was picked up by the secure system because he "sent it to a domain that does not use SEEMail" - in this case, Fairfax.

SEEMail is the agency used by Parliamentary Service for MPs and staff emails.

"SEEMail is an all of government secure messaging system that we subscribe to. SEEMail classified messages can only be sent to-from approved government departments and agencies," Parliamentary Service wrote.

KEVIN STENT/FAIRFAX NZ Speaker of the House, David Carter, is waiting on a report from Parliamentary Service about why they blocked an MP's email.

Parliamentary Service went on to confirm they had blocked the email because the attachment he was trying to send contained the words "SEEMail" and "sensitive".

Hipkins says this is a "clear breach of parliamentary privilege".

"That's outrageous, they have no right to be screening the emails being sent by Members of Parliament. It shouldn't matter where I got the information from, they've got no right to monitor my emails in the first place."

"I know that National is now cosying up to (Fiji Prime Minister) Frank Bainimarama, but that doesn't mean they can adopt his dictatorial, anti-democratic methods here in New Zealand," he said.

On further investigation, Labour staff found various other examples in the last few weeks where emails had been blocked - previously they've not had any issues.

"If someone leaks a government document to me and I send it to media that's my business," Hipkins said.

A similar issue was raised in 2013 when Parliamentary Services wrongly gave a ministerial inquiry emails between UnitedFuture leader Peter Dunne and then-Fairfax journalist Andrea Vance.

The then-head of Parliamentary Services, Geoff Thorn, resigned amid the fallout.

"What this has done is tipped us off to the fact that they're monitoring what we're sending in our emails, which is completely unacceptable," Hipkins said.

"Clearly they haven't learned their lesson from last time."

A spokeswoman for Parliamentary Service said they were working with Carter to pull together a report and couldn't comment any further.

A spokeswoman for Chris Finlayson, the minister in charge of the Security Intelligence Service, didn't want to comment while Carter is waiting on a report.