Public service bosses are checking whether their staff were responsible for a leak of a Cabinet paper on the cannabis referendum.
Earlier this month, the National party announced the details of the referendum, before Cabinet had made a decision.
At the time, the prime minister said she would not be ordering an investigation.
The Department of the Prime Minister said while it has not launched an investigation, it had reminded chief executives of the importance of Cabinet confidentiality.
It has "asked the chief executives of those agencies with access to the Cabinet paper 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," a spokesperson said in a statement.
"The leak of any Cabinet paper is a serious matter and it is right to remind agencies of the importance of confidentiality around Cabinet's decision making process," she said.