[UPDATE 5.30.19 - New Zealand Says Budget Leak Was Bungled, Not Hacked] 

The New Zealand government said Wednesday that a "systematic" and "deliberate" cyberattack was behind an embarrassing leak of secret finance documents ahead of this week's budget.

Treasury Secretary Gabriel Makhlouf said he had referred the matter to police on the advice of intelligence services.

Makhlouf said hackers attacked government systems 2,000 times over 48 hours in a partially successful attempt to obtain documents relating to the budget, which is not due to be released until Thursday.

"Somebody managed to penetrate and get some information, not the whole budget," he told Radio New Zealand on Wednesday.

Makhlouf did not know whether the cyberattack originated in New Zealand or offshore, saying that was a matter for police to determine.

He dismissed "absolutely" suggestions from the opposition National Party, which published leaked budget details on Tuesday, that the data was released accidentally by Treasury staffers.

"What I do have are these multiple, persistent, systematic, deliberate attempts to access our systems," he said.

Budget documents are a closely guarded secret and Makhlouf said the department was treating the security breach extremely seriously.

This year's document is the centre-left government's inaugural "well-being" budget, which it says is a world-first attempt to change the way economic progress is measured, putting people ahead of growth.

National leader Simon Bridges refused to say where the information he published came from but denied his party was responsible for any hacking.

"We have acted entirely appropriately. We have done nothing illegal," he told reporters.

The actual information released as a result of the hack is fairly mundane, including increased foreign aid and defence spending, as well as the establishment of a Mental Health and Wellbeing Commission.

[UPDATE 5.30.19 - New Zealand Says Budget Leak Was Bungled, Not Hacked]