Prime Minister Jacinda Ardern is not saying when she found out about an urgent attempt from the Government Communications Security Bureau to stop Treasury boss Gabriel Makhlouf from saying his department had been hacked.

But Ardern said this morning that Finance Minister Grant Robertson's job was safe.

The National Party is calling for senior ministers to come clean over when they knew about the GCSB's concerns, and why Makhlouf's "hacking" description - and Robertson's subsequent "hacking" description - wasn't corrected earlier, or stopped in the first place.

Last Tuesday the National Party released confidential Budget 2019 information two days ahead of Budget day, putting the Government on the defensive.

The Treasury sought advice from the GCSB about its computer system and was told that it was not a matter for the spy agency's cybersecurity unit because it wasn't hacking.

After referring the matter to police, Makhlouf met Robertson and then prepared a statement, in which he said the Treasury had been "systematically hacked".

But when GCSB boss Andrew Hampton was sent a copy of Makhlouf's statement just before it was released last Tuesday, he is understood to have made an urgent call to GSCB Minister Andrew Little in a desperate bid to change the language.

Ardern said today that how and when that message was passed on could form part of the State Services Commission investigation into Makhlouf, and whether he misled the Government.

But she would not say when she was told about the phone call.

"What will be most helpful here is we allow the State Services Commission to pull together some of those timelines and information," she said.

"I've given an undertaken that I'm withholding any judgement until that work is finished."

Asked if Robertson's job was up in the air, Ardern said: "Absolutely not."

A spokeswoman for Robertson said that the minister was not aware of the GCSB's phone call when Robertson's statement - repeating the Treasury's description of a hack, but also naming the National Party - was made public on Tuesday, May 28, about 8.15pm.

The spokeswoman would not comment on when Robertson found out about the GCSB phone call.

The GCSB and Little have also declined to comment.

National Party deputy leader Paula Bennett said the phone call showed that senior Government Ministers knew they were releasing false information to the public.

"It is inconceivable that the GCSB Minister didn't immediately phone Finance Minister Grant Robertson and the Prime Minister to give them that information."

National has accused Makhlouf and Robertson of smearing the National Party by knowing all along that no hack had taken place but describing it in that way anyway.

Robertson has rejected that, saying he was following the advice of the Treasury in calling it "hacking".

Makhlouf has not commented since he gave media interviews last Wednesday.

Bennett said Robertson needed to "front up" about whether he knew about the GCSB concerns before his statement was released.

"[And] if Mr Robertson received the information from Andrew Little after he released his statement, he should have immediately corrected it."

National Party staffers had been able to access Budget information simply by using the search function on the Treasury's website.

Treasury had set up a clone system with Budget information that it had not realised was accessible.