A hunt is underway to try to find out who leaked a confidential Government document to the National Party.
1 NEWS can reveal the Prime Minister's officials have ordered public sector chief executives make sure their staff did not leak the Cabinet Paper on the cannabis referendum to the Opposition.
The National Party revealed key aspects of the referendum before the Government could announce its plans.
Prime Minister Jacinda Ardern told the public this month that she did not see merit in holding an inquiry into the leak.
"I should focus on getting on with the work at hand, we have not experienced the leak of a paper directly before and I don't know that an inquiry would actually answer the question of how this came to occur," she said at her post cabinet media conference on May 6.
"I do not believe it came from our Cabinet."
However, the Department of the Prime Minister and Cabinet [DPMC], which serves the Prime Minister, has contacted public service chief executives and asked them to investigate. Some public servants had their emails searched, 1 NEWS understands.
DPMC told 1 NEWS it "reminded chief executives of the importance of Cabinet confidentiality".
Public service chief executives were asked to "assure themselves that any staff who accessed or were provided with the paper were entitled to do so and that they handled and managed the paper appropriately" by the department.
Today, when asked by 1 NEWS, the Prime Minister labelled it an "operational issue, and not a matter for me".
Despite it being her own department, the Prime Minister distanced herself from DPMC's request for chief executives to look into the leak.
"I certainly haven't ordered an investigation, it's up to chief executives if they choose to make there are checks in place to ensure confidential information is handled appropriately. It's chief executive's prerogative if they choose to undertake that work.
"Chief executives may well go through to ensure that their own processes are protecting Cabinet papers. That’s a matter for the public service and the state sector."
The National Party's deputy leader Paula Bennett told 1 NEWS: "The fact that chief executives have been told to 'assure themselves' that the cabinet paper was handled appropriately makes it clear an investigation is underway".
"But rather than pointing the finger at officials, the Prime Minister should also look closer to home.
"National has received many leaks from the Government, which is helping us hold it to account. It shows the Government's policies and decisions have people on the inside worried, as well as the general public."