'He's lying': Simon Bridges lashes out at Grant Robertson after hack claims

National leader Simon Bridges has lashed out at Finance Minister Grant Robertson, saying he is lying about National receiving information after Treasury was hacked.

Bridges said the National Party had not been involved in illegal activities.

"We have acted legally, appropriately, without any hacking or anything approaching that by the National Party or indeed what Grant Robertson is saying, where he is effectively saying that is how we got it. He is wrong.

"What annoys me here is that it should be Grant Robertson here right now, explaining and fronting up. He is misleading New Zealanders, in fact, I would go as far as saying he is lying," Bridges said at a fiery press conference on Wednesday morning.

"He is smearing the National Party falsely with what he is doing and he is overseeing gross incompetence in Treasury right now and over the last 24 hours. That starts at the top with him."

Robertson said on Tuesday the hack was an "extremely serious" matter and called on the National Party not to leak any more information.

"We have contacted the National Party tonight to request that they do not release any further material, given that the Treasury said they have sufficient evidence that indicates the material is a result of a systematic hack and is now subject to a Police investigation."

Bridges says he knows how the information was obtained, but wouldn't elaborate. He did, however, confirm the information had not come "as a result of hacking".

The leader called the Government incompetent and embarassed. He believes they were trying to "gag" the opposition.

"The reality is they are incredibly embarrassed… they are lashing out. They are having a witch hunt on the National Party," said Bridges.

He said the Treasury had got "many things wrong" and wanted them to prove their statements were accurate alongside Robertson.

Hack of Treasury's systems

On Tuesday, National leader Simon Bridges revealed details of the Wellbeing Budget - two days before the official announcement.

But Treasury says there's sufficient evidence to show its systems had been deliberately and systematically hacked, and had referred the issue to the police on advice from the National Cyber Security Centre.

"Yesterday afternoon, we discovered multiple and persistent attempts to gain unauthorised access to Budget information," Makhlouf told The AM Show on Wednesday.

He said there had been at least 2000 attempts.

Makhlouf said that parts of the information had been in the process of being uploaded, but that information wasn't publicly available.

"I have instigated a review to check exactly what has happened. But the information I had yesterday confirmed there was no accidental release of the information.

"There is a lot of information that is uploaded and it takes time to upload. So there was a process, but it wasn't open to the public."

He couldn't tell if the hack had come from overseas or from within New Zealand.

Makhlouf said he had no evidence the whole Budget had been extracted from the Treasury's systems.

"We don't believe anything else of material nature is out there, but we can't be 100 percent certain.